Wheels, brakes, suspension sequence

Thanks for the input so far! Plan to keep the slant 6, had a serious valve job and tune and runs nice. Never intend to swap out motors, maybe a rebuild of current eventually.
But nice and smooth up to about 55 mph. But maybe I had it bass awkwards- get the discs and bolt diameter figured first, then to suspension, and finally wheels.
As I feared its kind of a package deal- each part won't succeed long w/out the others.but that sounds like $5k in one fell swoop. Ouch.