Brad, your First Ckass! The 455 crankshaft done by a "chevy" machine shop has never been right. I have a high end 10 10 crankshaft. I think it may be the route of the problem. Need a good foundation to build a solid home, A 455 is no different! Stay tuned!
Where's the heat going while cruising? Cars have thermostats to keep the engine hot at any speed. Pull over on the freeway and place your hand on the engine block. I bet it's hot.
There shouldn't be any more heat in the clutch while cruising if it isn't slipping. That's why I asked about the free play at the top of the pedal travel. If there's no free play, the disc can be releasing slightly causing slippage.
