69 Dart budget reality - Front end!

Folks, please impart some knowledge on an old guy that is doing my first Mopar. My brother is kind enough to allow me one of his 69 Darts for a project.

I will be using a rear suspension from RMS because I will have pretty large meats on the rear end and that seems the simplest.

In an effort to keep the initial budget down I am considering a rebuild of the stock K member front end for budgetary reasons until I get the rest of the car the way I want it. Here's the question:

I have been told that the newer cars had larger ball joints and disc brakes that would swap directly in from a donor car - is this true, and where might a guy find a write up on someone else's labor and info?

I plan to use a 360 cid (~500 hp) and a 727 if that matters.

Also: how much difference will torsion bar size make - if changing that is even feasible?

Thanks folks!