Hi, new guy here. Recently purchased a 1967 GTA S code fastback built in Metuchin in January of 67. No drive train, looking for the correct engine. Been doing some research, but could use some help. What casting numbers should I be looking for on the block, headers, and manifolds? Seems like up to 6 month prior would be OK, but I've also heard should be within 2 months for date code. Also, the third letter of the casting number is confusing me, should it be "Z" for mustang or is other designator s OK? I passed up an "M" the other day. Also, my understanding is that the GT exhaust manifolds and Headers are unique, but the block is the shared with non-GT. Any help appreciated! I'm not doing a concours resto but I'd like to be right with the engine.