Join Date: Sep 2000
Location: Washington, Michigan USA
The pad stamp indicates that the block is a warranty replacement, built in June, 1970 (these were generally supplied as short-blocks, re-using the original heads). The heads are wrong - should be 3927186 (same casting number was used for SS350's, but they used smaller [1.94/1.50] valves, and later SS350's used the 3947041, also with the smaller valves) - the 7186 heads for the DZ engine had 2.02/1.60 valves. The 3991492 heads you have were used on 1973 Camaro/Corvette 350's. Looks like you have a 302 factory replacement short block with heads from a 1973 350.
'69 Z28 Fathom Green