Hi all. I’m new to the board, but not so new to my '72 GS 350 (bought it in '94). It’s basically stock except for a 2-1/2 manifold-back exhaust and Flowmasters. I’ve been getting the itch to do a mild top end rebuild project and gain some much needed HP. Nothing crazy since it sees light street use only. One area for improvement I’m considering is targeted porting/polishing of the cast heads. I recently picked up a spare set (casting no. 1243452) which I understand spanned several years. Since they came cheap I’m not afraid to try porting these on my own, once I learn more about how to (and how not to) for the performance improvements I’m looking for. Before I disassemble and have these cleaned/magged, I’d like to know more about these heads: 1. Their production spanned '72 - '80 from what I’ve read. Are any years of this particular casting code more desirable? 2. How do I know what year these particular ones were produced? Each has “A•5” marked on the top left side as well. 3. How do I know if they are smog-equipped, and if they are, how do I “un-equip” them? ;-) 4. In general, is it worth me working on this particular set, or are there other more desirable (so harder to find) SBB heads that I should be searching for? I’m not much interested in modifying the heads on my car because a) it’s together/drivable now, b) if I sell the car I’d like to give the next guy the opportunity to restore it, and c) in case I mess up the heads I won’t spoil b) by doing so. Thanks for your help!