first off, there's alot of things you can do to sorta modernise without changing the frame. them little wheels just don't look right.

i thing the rear end from a p-30, or even some old step vans are 10 hole, and bolt up. this give you a single speed rear, with modern brakes and a much higher top speed. an overdrive tranny gets you even higher top end, but if you get too tall a ratio the engine will cuss at ya and maybe not want to go along with the program. it could leave to the overheating problem stovebolts are famous for.

65 mph is plenty i'm thinkin'.
then,

there's the spanky solution. drive slow and let folks marvel at just how good yer ride looks, and in spankys case, that's pretty good!

check out is website.