I recently picked up a very nice numbers matching 1969 Z28 DZ car. Have been really pleased with prob 90% of the original parts there with correct date codes. First week May 69 car. The only disappointment was the motor must have had a problem around 1975. the heads were replaced with a set of over the counter straight plug 492s, F 29 5 dated. I can fix that with a set of A,B,C or D 186s. The question I have is do the original 186s have screw in studs and guide plates from the factory in 69? and I assume they were all 2.02 valve heads. Thanks for everyones help. You guys are a wealth of knowledge.