C4 with a dynamic full reverse VB, H servo, Deep pan , a motor home style cooler and i've never had an issue. I've gone 12 rounds @ Norwalk on a wednesday night without a hiccup including a hotlap or two. I don't have a gauge for temps but i've enevr seen any fluctuation in converter RPM. Speaking of converters, I second the vote for getting a custom Coan, or hughes converter. The guys that go from a 5 speed, to a C4 and the cars slow down, either slap in a cheap TCI converter like i did, or just flat got the wrong converter. I got a (good deal

) on a TCI converter and it was the only thing keeping my car from the 10's a few smackdown's ago. Also I hated my C4 til I put the full reverse VB in it.
I had 28" tires and 3.55's and the thing was a highway screamer with my old 302 paxton combo. My speedo was off but I had no problems with traffic or 70+mph cruises.