Looking for advice on a '71 Demon

Schumacher creative offers mounts for small block to /6 k member, they work well from my experience, swapping the k frame is of course simple enough too. T bars from /6 will be ok with a small block, brakes are always a concern IMO, as they were often marginal at best from the factory, also not overly complicated. Assuming you are somewhat mechanically inclined as an E body owner already, you shouldn't have any real problems with anything on an A body