The 454 will bolt in on 350 mounts, they are in the same location. A decent set of headers should clear all your accessories. If your current radiator is keeping the 350 cool, it should do OK in all but extreme conditions with a 454. Same with your TH350.

Devin

If you can't hose it out it ain't a truck

55 3100
63 Corvair Monza
64 El Camino
72 240Z
01 Suburban