When all is said and done, figure about $6,000 plus for a good handling aftermarket subframe.
On the other hand you can (as I plan to on my '67) run the ATS (
www.t56kit.com) extended spindle, your stock UCA/LCA, del-alum UCA/LCA bushings, aftermarket front springs and good shocks, a 3rd generation IROC steering box and a good swaybar and (assuming everything else is in good condition - wheel bearings, ball joints, steering linkage, etc.) have a very nice handling front suspension for about $1,500 to $2,000 depending on the specifics of what you do (particularly shocks).
Tubular control arms don't contribute to good handling and aren't needed. The bolt on R&P systems won't perform nearly as well as a good box.