No, they will not work. The input shaft has a different pilot bushing/bearing diameter and the transmissions I'm pretty sure they cannot handle the torque of a decent V8. You will have to find a better T-5 (World Class at least) to be able to handle your engine with any longevity.
Thats cool a guy told me you could change the pilot bushing and they would work. I didn't really think they would or they would all be gone.
The lower first gear would be nice to bad.
What is the first gear ratio? Most World Class T-5s have a 3.35 first gear which is about as steep as you want. With 3.50 or better gears out back it is almost too much because you end up shifting way to fast into second. They work great with a highway gear (2.79-3.00) because that is what they were intended for....to boost low end performance without sacrificing highway driveability.
You can do it (I am not recommending it though). Forget about it if you really have 350 hp. You need a pilot bearing/bushing from a ranger (80's with a 4.0???)-- do a search over on the carbdford forums (http://www.carbdford.com/forums/). As for 1st gear being that low-- it's crap. I already hate the 3.35 1st in my t5. Next T5, i'm looking for the 2.97 gear. The gap between 1st and 2nd sucks as is.