The USCartool subfame connectors, Hotchkiss-tuned Bilsteins and Firm Feel transformed my 69 Coronet. You are on track. The other change that made a huge difference was the install of late model bucket seats and the Momo JPS reduced dish and diameter steering wheel. Don't underestimate ergomonics. I have stage 1 ff and would go with stage 2 nexxt time. Stage 3 may be a little stiff for a smaller steering wheel. Personal preference here.
What this guy said! Sizing down the steering wheel from a stock 16" to 15" aftermarket wheel will help some, but I tried a 13.5" and it was way too small. I also have Firm Feel stage II in my '68 Satellite and it's actually a little too heavy feeling for me. I think stage III for a street car probably wouldn't be to your liking. Note that on the Firm Feel website they describe the stage I as having the cop car feel. This stage I is firmer than a stock power steering for the roadrunner. Stage II is not bad, but just a little more than the power steering in my honda or my wife's Nissan Murano and WAY more than the power steering in a stock Belvedere and old '67 chevy I used to have.
You're on the right track with the torque boxes and subframe connectors. Those really made my car feel a lot more solid. Consider the subframe connectors from Global West. They are tubular, which are stronger than square channel, and weld at each end instead of along the entire floor board and are what I have in mine. They're excellent. You can tell a noticeable difference. You've already got sway bars front and rear so that's good.
I have .092" torsion bars in mine right now and they were a good replacement for my stock .088's but they could go to .096 and it would be a bit better. Don't go above 1.0" torsion bars or you'll jar your teeth out when driving on the street. You want a little bit of compliance. For example, Hotchkis offers 1.03" bars, but these are VERY stiff, more than 1.0" bars. For every .004" up in diameter it increases stiffness by something like 14%. I would go with either .096" or 1.00" here! Don't forget the torsion bar boots and clips.
I also have Hotchkis UCA's and their steering rods as well, which are supposed to reduce bump steer and allows me to dial in +4.5 degrees caster. The Hotchkis UCA's are not noticeably lighter than my stock UCA's, which surprised me. I would do these UCA's and steering rods as last priority. They also offer rigid heim joint strut rods. I had them on at first and then removed them and put on new rubber bushing stock strut rods. The Hotchkis ones felt awesome on smooth roads, but in the bumpy streets of san jose I was afraid it would jar the car too much.
What leaf springs will you use in the rear? Stock should be good if they're not worn out. I wouldn't go for the Super Stock SS springs for handling and those make your car sit up higher as well. Those are supposed to be great for drag racing though.
