Rearend gear selection

wow i dont think you will find a 295 width tyre will fit under a darts arches without leaf relocation and mini tubbing. 245 at best

personally, i would re think what you want from your car, as everyone says, your a little short on cubes, so i would be looking at a cruiser rather than racer, but who am i to say whats best for you.
yes a looser converter will help, but without knowing weight of car, cam and carb sizes, head work, and intake, its best to suggest you talk with a converter company
do some chassis work like tie in the frame, and possibly look at ss springs out the back
a nice free flowing exhaust system will help, alot.
and a nice dual plane manifold and matched 4 barrel too.