Asking a couple questions-will my A body corner?

15" won't cut it, sidewall is too big, they don't really sell good sticky modern compound tires until 17".

Really depends what he is doing. My mustang handles damn good with 15" rim/tires

If this is just a street cruiser keep it simple.

Make sure front end is in good shape. Convert to disc brake if that's what you want
1" bars
I like fresh leaf springs too. Xhd from espo will do
Good shocks.

Those few things will help big time.

Second stage could be.
Frame connectors
Front and rear sway bars.