While a V8 sounds like a fun project idea, you'd never get the thing fit in there. Unlike a car, machines are designed around the engine choice with no room to use anything else. Even if you did shoehorn it in there, the thing would have way too much power as Lavoy points out.
Deere did this with the 435. They took the back half of the 430w as-is and put the GM 2-53 diesel in from the 440 to produce a haying tractor. It had a 1000 RPM PTO to run a larger baler. As it was meant, it was a great tractor. Unfortunately a lot of them had their ring and pinion gears worn out in a hurry as farmers figured out that one could pull an extra plow bottom or two with that extra HP.
Not only would you have too much power with a V8, but a completely wrong power curve for the machine to actually do the work properly. So, even if it didn't bust everything else in the powertrain, you'd find it really difficult to actually use.
Still, I know what you're thinking of: Those Ford N series tractors you see at shows where someone yanked the flathead 4 out for a flathead V8. Those *do* look really cool, but they're not machines that are used for anything other than running around at shows.
later!
Stan
