Bigger bars are going to make it ride firmer. How much firmer are you ok with? For my 65, I got the 1.06 dia bars from Firm Feel along with rear springs, Bilstein shocks all around, front and rear sway bars, upper control arms, adjustable strut rods, 9/16" tie rods w sleeves plus some other stuff. I got a $3k tee shirt from them and they gave me the suspension stuff for free. LOL! My intentions for the car are track events, auto crossing, some drags, fun curvy road driving etc. Its also getting quite a few structural upgrades too. Frame connectors, torque boxes etc. Poly bushings can squeak. I have no problem with my car riding stiff when I get it done. My daily driver is am 04 Dodge 3500 Cummins dually so I'm used to being in something that doesn't ride like a Caddy. What are you willing to put up with?