the one that's on it had been resurfaced when i rebuilt the engine 25,000 miles ago. the shop i took it to told me they had to take off a lot of material to get it straight. i also read this may have been what caused it to warp again. the one that i measured is a spair set off a 292. i don't know how far out the one that's on there is. i was wondering about making some copper shims out of .025" sheet copper. i was thinking about making one piece that would strech fron 4 inner exaust ports and middle two intakes. has anyone ever tried this or is it crazy.