Detroit Eaton springs can build custom springs with softer ride and any ride height you want, add a power steering kit like Craig has going and you will be money ahead and still have the truck you want. What you don't want is R&P steering with a straight axle. If you go with a front end kit, what about the rear axle? It will still be rough riding, with new springs all around, the whole truck will be nicer. Does the kit you are looking at have new brakes? are they compatible with the brake system? Will the wheel bolt pattern match the rears?

Up-grading what you have is a lot easier then replacing in my opinion.

1937 Chevrolet Inline-powered Streetrod