1970 Dart Swinger - father and son project

Question, why put a V8 in there and make it nose heavy when there is a perfect slant under the hood to buile power off of?
I have had that thought myself and is also why our primary goal is to do body work and get it on the street. I need a radiator, was looking at the $80 aluminum ones available on the net and wondering if they are any good. Hoping to get some feedback on that here. This beast has the 198 cu /6 rated for 125 HP, and I am uncertain how to go about these as it is my first. On the other hand a 318 or 340 is not that much heavier and pushes a lot more horses, I do understand that a big block in these boys makes them difficult to turn! Any of you out there developing 198 /6's for power? where did you start and where did you end up? I would love to hear from you as I have heard a few stories of /6's with serious HP, just not certain HOW.