Frame or chassis options for A bodies
^ Do you really need all that kit?
No one really
NEEDS it.
But he's not wrong. If you just outright buy the Hotchkis TVS kit and then add what's missing you're not too far from a coilover conversion. At least for the front suspension. Now, you don't need everything in the TVS and there are places where you can save money to make the difference more dramatic, but either way you don't end up with a rack and pinion. I had my entire set up all laid out and priced and came out cheaper to do my entire car than it was to just get a RMS Altercation in the front. But I did all of my own work, mixed and matched some parts, and bought a few pieces second hand that were "new in the box" for half the cost of new (my Flaming River 16:1 manual steering box, for example).
And of course you don't really need a rack and pinion, it won't make you any faster. Feels nicer though. But if that's what you like, then the full coilover conversion is really the only way to get it. Otherwise your stuck with the older style steering box.
Same idea with doing the coilover conversion in the front and a 4 link rear vs doing the full aftermarket chassis. If your paying someone to do the frame connectors, torque boxes, install the 4 link etc, then you'll rapidly approach the cost of the full chassis kit. But do the welding yourself and you'll save thousands. But if the plan is to send the car to a shop, cutting the big $15k+ check for everything might not be the worst way to go. It'll still cost more money, but the shop won't have the car nearly as long and you know everything will work together.
But you don't need it. lilcuda's '68 Valiant has lapped portland international raceway as fast a C06, hitting 160mph down the straight, it's a torsion bar and leafs car. Tomswheels ran the Goodguys autox faster than some $150k Camaro with his '69 cuda convertible, and he was still running $14 Gabriel shocks. I'm guessing the $150k Camaro was a bit easier to drive though. And his Valiant is faster than that and still a torsion bar and leafs car, it won SCCA CAM events, finished 2nd to M. Pozzi at San Diego, 5th in the CAM nationals west, etc.
Heck I heard Tom was selling his car, you could buy his for less than it would cost to go to a full chassis. Or to even build his car...