As martin suggested, swapping out the torque tube rear, putting in a newer 6 cyl (235 or bigger) and then adding front disc setup and you will be more on the way to 65-70 mph and being able to stop!
Going is only a small part of it, you want to be able to stop and also have it handle ok at the higher speed! (may want to look at upgrades to leaf springs as well)
If you are looking at a 50's V-8, the main difference as far as looks between a 283 and a 1st gen 350 is going to be breather tube, valve covers and intake manifold (oil filler tube in front of the intake manifiold). Valve covers and intake are easy, breather tube (road draft tube) is probably not something you would want to retrofit onto a newer block anyway, you would want to use a PCV valve.
