Ok, I know I am risking being proved a fool by disagreeing with you Panic, but Boring the Knuck heads for the Pan firering is indeed like shaving the heads .200". Both the Knuck and the Pan share the same stroke, rod length, and piston compression height. Unless the distance from the centerline of the crankcase to the cylinder base gasket surface on the case is different from Pan to Knuckle (and I don't think they are), that means the top of the piston is coming to the same place on either. On the Knuck it is coming (roughly) to the head gasket surface on the cylinder. On the Pan it is coming to the top of the firering, or .200' above the head gasket surface. Obviously if you remove the firering, you will need to add a .200" stroker plate to keep the piston from coming .200" out of the top of the cylinder. But if you bore the Knuck head for the firering you have lowered the head .200" in relation to the dome of the piston as compared to setting on top of a Knuck cylinder. Am I wrong?
The pushrod angle when using Knuck heads with shovel cam and lifters is far better than the angle with stock Shovel heads. In fact, just eyeballing the Knuck head/ Shovel lifter block combination (with no covers), the pushrods appear to be perfectly straight in line with lifters. The problem is that the lifter blocks are machined at angle for the cork to seat on, that is different than the angle of the lifters. (Come to think of it, maybe all it would take to make the covers seal would be to re-machine the seat for the cork in line with the lifter.)
As to how good (or bad) and engine with Knuck heads and Shovel cam and lifter blocks will run, all I can give you is my own personal experience. AMRA "Street Racer/FL" National Champion 1986 and AMRA "Pro Stock" National Champion 1987. Throw in the 7 National Record certificates hanging on my shop walls, and I think you would have to admit the loss of performance from mismatched parts is within acceptable limits for most street use.