[Hozer 88GTConv]

I know the serpentine belt on 351's runs opposite of a fox 302. That's really the only pita about 351 drop in's. You can't use 302 accessories. Or at least not without some creativity.
So, you 'd just have to do some hunting around to get the accessories.
I think the stock emissions crossover tube on the back of the heads might just be a little short. But everything else has a hose or is flexible enough to be adapted to a 351.