If you do a small block, I'd suggest 360. The extra cubes and torque would be welcome. Plus if you want to hot rod it, a 360 is a better starting point.

For brakes, the front's do 70% of the stopping. An upgrade to discs up front would get you a lot more benefit than changing the rears. Look at MOPAR Action's web site for brake choices using later year OE parts or Master Power Brakes for pre-packaged kits.