Worth a 351w swap

It's not hard to put a 351 in a 98. There are things you'll have to work around like the speedometer. I believe 98 is electronic. Getting the factory tach to work is a different story. No idea how. A digital dash would solve those issues. The next things are a swap pan and 351 swap headers. Easily acquired. It all depends on budget. The work isn't hard.

This is a difficult one to answer and has a lot of potential twists and turns depending on how you answer the following questions. I'm not an expert, there are probably better folks on here to answer these details than me, but I've helped two friends do the swap with their '94s. Your scenario is a bit different since it's a '98.

1) Do you already have the parts to Windsor V8 swap an SN95?
2) Do you already have the 351 specific parts to make it work?
3) Do you have a significant budget for the parts?
4) Can you fabricate what's needed?

I ask this because there are several different routes to go. Having a 351 engine is only half of the battle. The following are some hints for each scenario:

If you already have parts from a '94/'95, such as the accessory drive, T5 trans, K-member, harnesses, H/X pipe, driveshaft, exhaust hangers, and trans crossmember, then you just have to pickup the 351 specific parts such as oil pan, headers, intake manifold, and distributor. I'm not sure if the V6 K-member is the same as the Windsor V8 K-member. Your car being a '98 also raises questions about the spindles since they changed for the modular V8s due to a lowered position of the steering rack. Hood clearance is also an issue for 351s. Some people claim to have fit a 351 under the stock hood by using drop or solid motor mounts. No matter how we played it with stock or energy suspension mounts, we couldn't get the GT40 intake under the hood without having the oil pan contact the steering rack. This required a fiberglass hood with a cowl bump. A lot of this depends on the intake setup, but squeezing it under a stock hood isn't realistic depending on the intake manifold used.

If you have a good budget for this, you can make the swap a lot easier by going with a tubular K-member, but that gets pricey and usually requires a better front suspension like tubular a-arms and coil-overs - probably a good upgrade anyways. You can also go with aftermarket accessory drive systems that fit tight to the engine, like a street rod setup, but those get expensive, too.

The exhaust has become really tricky. The market has contracted quite a bit in the last ten to fifteen years. Hooker used to make a set of drop-in 351 shorties that fit the factory Windsor V8 H-pipe and were production on Saleens. They just discontinued them earlier this year after the prices jumped up to $650 un-coated and $750 ceramic. It's no wonder why they killed them, I don't imagine they sold many at those prices. There might be other options out there, but they are becoming few and far between.

For a lot of these parts, you could potentially use Foxbody items, but then you're dealing with adapting foxbody parts to fit a V6 SN95. I've never done that, so I can't comment. From what I've read it is do-able, but there are some tricks to foxbodying an SN95.

If you can fabricate items like exhaust and crossmembers, than a lot of this become sort of moot. WIth that capability, you can pretty much make anything work or engineer what you need from scratch as you go. (My fabricating days are over, so I'm always looking for the bolt-on path.)

The other question is your car's suspension and rear axle. You'll definitely need to upgreade these for the weight and performance of a 351. You can probably get away with the V6 axle if you're easy on it, but even a mild 351 will eat it up if you put the hammer down regularly - like I would.

It sounds like you already have some good experience based on your other cars and projects. My advice would be to list out what's needed for a 351 swap depending on the path you are going to take, check availability, and total it all up to see if it's really worth it or do-able.

The first swap I did was a mild '90s period correct 351 build. It runs ported 3-bar iron GT40s, a lighting GT40 intake, a mild hydraulic roller cam, a T5, and 3.55s in back. Mostly stock or slightly upgraded suspensions parts. It's probably makes something like 340 HP at the flywheel. It's a really fun cruiser. He never drag races or hard launches it due to the T5, and pretty much can't go WOT in 1st or 2nd without blowing away the 245 tries due to the low end torque of this motor. We've toyed with idea of going to 3.27 gears and wider / stickier tires, which would probably work better with his T5 3.36 first gear. This build wasn't too bad a the time with the most expensive items being the shortly headers, lower intake, and 351 EFI distributor.

The other swap was a 408 stroker with good TFS heads and intake, realistically making around low 400 HP due to the intake manifold with a LOT of mid-range torque. This combo got a TKO600 since it would kill a T5 in no time flat. He had custom long tube headers and exhaust fabricated by a race shop who also built up the 8.8 to handle the torque. It's great at the track with slicks, but scary on public roads. Even with drag radials and a straight line oriented factory-style suspension, it wants to jump sideways in 3rd gear when you drop the hammer. He spent almost as much on the exhaust, trans, and rear end as he did on the motor itself.

I don't want to discourage you in any way, but it's important to be realistic. Having a 351 is just the beginning. If you already have a GT or a Cobra with a 302, then it's a much smaller step up than doing this from a V6 starting point - and a '98 V6 might come with some additional challenges.

Good luck, brother! =)