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Being that you didn't say you were going to use pump gas only then you have options. Ford Motorsports SVO crate engines are available in up to 460 cubic inches with up 560 horse power. If you have a 351M or 400 then the 460 engine will bolt right to the transmission you have (motor mounts may need to be changed). I can't say that your drive line has a chance to handle this engine, but you are probably going to break things even with 385 hp in a 24 year old truck.
Want more? Buy seperate components from Ford Motorsports and build up to a 705 cubic inch engine. I don't know what prices these sell for, but be prepared to see prices exceed 5k.
FYI: All of the Ford Motorsports crate engines are assembled at the Ford Windsor or Cleveland engine plants with all new parts. In other words these engines are new and built by Ford.
Some of these engines and parts are way beyond what the regular truck enthusiasts will desire. Still there are enough people around that will use them in customized trucks to consider them as options for trucks.
If you've decided to go with the 385 class of engine, pass on the 429 since they can be a little hard to find. Get the 460 instead, which are everywhere and pretty cheap, then dump your 5k into the motor. With a stroker kit, head work, cam and a little engine work, you can have a 600 horse fire breather.