Horse Sense: As popular as the 351W-in-a-Mustang swap is, Ford waited until the last year of the Mustang's pushrod engine to offer a production Mustang with a 351. Only 250 units of the '95 Mustang Cobra R were produced with the 351. That R's engine produced 300 hp at 4,800 rpm and 365 lb-ft of torque at 3,750 rpm.
Cubic inches are like money. Having enough to be comfortable is nice, but having a lot is better, and having more than you know what to do with is just right. The 5.0 is a potent engine--just ask any 5.7 Camaro owner--but when it's time to rebuild or you just want that competitive edge, some extra cubes are in order. Yes, there are numerous 302 stroker kits on the market, and they have their advantages (which we'll talk about later). But if you really want to go for the gusto, then you should consider moving to a 351W. It has more cubes in its stock form than you can comfortably--or affordably--extract from a 302-based engine, and you can stroke it well beyond 400 cubes should the need arise.
If you plan to go racing with your 351 or just want the added beef for a stroker engine, Ford Racing Performance Parts' M-6010-N351 block is the way to go. The cast-iron block has a 9.5-inch deck height and has four-bolt mains on journals two, three, and four. It's substantial enough to produce up to 434 cubes if necessary.
If you've been thinking about a 351W swap but didn't know where to start, you're in luck. We talked to some of the leading swap experts in the industry.
In the following pages, we'll discusss 351W/Fox chassis swaps and their advantages/disadvantages versus a 302-based build. We'll also clue you in to all the parts necessary to get the job done right--from the oil pan to the top of the intake manifold. Now let's get rich!
As swaps go, the 351W/Fox chassis swap is relatively simple, with no fabrication or butchering required (the same is true with SN-95 cars). The stock motor mounts will work, as will the front cover, the radiator (if you plan to build a mild 351), the shroud, the water pump, the pulleys, and all of your accessories when the proper brackets are used (more on that later). Unfortunately, just about everything else needs to be replaced, which will add to the cost of your project.
Beginning with the bottom of the engine, the first thing you'll need is a different oil pan. The 302 uses a rear-sump pan, while the 351W uses a front-sump oil pan, which necessitates a new pickup. If you're going to limit your driving to the street, FRPP offers a complete oil-pan kit (PN M-6675-A58) that includes a 5-quart (stock capacity) rear-sump pan, a dipstick, a tube, and a pickup. The oil pump and drive are not included, so you'll have to purchase these items separately. For a street application, FRPP recommends a stock-replacement oil pump (available through Melling), while a street/strip engine with looser bearing clearances (0.0025-inch) can use an FRPP M-6600-B3 pump. An FRPP M-6605-A341 driveshaft will work in either instance.
If you don't want to build the engine yourself, and you want a quick and easy solution to your cubic-inch deficit, then FRPP still has the answer for you. The M-6007-C351 is a complete engine assembly from the pan to the intake manifold, and it includes such niceties as aluminum GT-40 cylinder heads, a hydraulic-roller cam, roller rockers, and a distributor. It already fits Mustangs, and it produces 362 hp (with a 780-cfm intake). Get an EFI intake system and you'll be good to go.
For street/strip applications, Canton offers a rear-sump, 7-quart oil pan (PN 15-670, with a pickup sold separately under PN 15-671). Moroso also offers a 7-quart oil pan (PN 20520) with a built-in windage tray and scraper that fits '81-'97 Mustangs, '81-'88 T-birds, and '81-'86 Capris (pickup sold separately under PN 24514).
The 351W also has a different balance than the 5.0. The 351W requires a 28-inch/ounce unbalance, while the 5.0 uses 50-inch/ounce unbalance. This means you won't be able to reuse your stock 5.0 flywheel or harmonic damper on your 351W. FRPP offers a billet steel, SFI-approved, 157-tooth flywheel (M-6375-A302) that will work. And assuming you wish to use the factory serpentine-belt system, you can use the FRPP steel damper (PN M-6316-C351), along with the M-8510-B351 or C351 spacer, which creates the proper alignment with the serpentine system.
According to Rod Kack at FRPP, you can also use a damper from a '75-'80 302 or 351W engine, but you have to make sure you get the right one. There are two different bolt patterns and three different lengths, measured from the mounting face to the end of the snout: a 3.000-inch with a three-bolt pattern, a 3.400-inch with a four-bolt pattern, and a 3.950-inch with a four-bolt pattern. This last one, according to Rod, is the only one that will suit your needs if you want to retain the serpentine system.
As mentioned earlier, the stock motor mounts--if still in good condition--will work. But, because the 351W is 3 inches taller than the 302 (measured from the bottom of the stock pan to the top of the stock valve covers, the 302 measures 20 3/4 inches, while the 351W measures 23 3/4 inches), you could encounter hood-clearance problems with fuel injection. HP Motorsport offers solid motor mounts, which lower the 351W by 3/4 inch in the engine cradle, improving both hood clearance and center of gravity. According to HP's Paul Brown, you shouldn't encounter any clearance problems down below as long as you're using the FRPP 351 pan, stock crossmember, and rack. Paul also maintains the solid mounts aren't too severe on the street as long as the factory rubber trans mount--or aftermarket polyurethane mount--is used.
In any case, you may still require a cowl hood, so keep this in mind when tallying your expenses. If you're beginning with a car that was originally equipped with a four-cylinder or V-6 engine, or you just want to use stock-type motor mounts, George Klass at Coast High Performance recommends certain Ford motor mounts (PN E7ZZ-6038-E and E7ZZ-6038F). These are factory convertible 5.0 motor mounts that feature more reinforcement and therefore are stronger than standard 5.0 motor mounts.
The front cover from your 5.0 will work, along with the water pump. But if your water pump is original, it's probably not a bad idea to purchase a new unit from FRPP, or aftermarket manufacturers such as Edelbrock, Stewart, or Evans Cooling.
FRPP Serpentine Spacer | 
FRPP Damper | 
HP Drop Solid Motor Mounts |