68 gto engine code

i have a 68 gto that needs to be restored, and all numbers match except the engine. the only numbers on the engine that i can find is 104196 and below that is code YH. i could not find a YH on the code list and was wondering if anyone could help me with the numbers. thanks

repling to my own message. just found a code list that has a 68 code YH and shows that it is 428cid and 375hp. i was wondering if anyone knows if this correct or not? thanks

if you look down the passenger side of the block nest to the timing cover you will find the find the # stamp there.

YH in 1968 was a 428 block

thanks for the reply. i found out the same, but i was told that gtos did not come from factory with a 428, but could be dealer installed. is this true or not? thanks