I'm looking at the production tables in the Volvo P120 book by Günther and Wolf. There are some discrepencies within the tables themselves, and I may have reached a too-hasty conclusion last time. ???

There's a B18B listed for the M production P120, the '67 model year... but it does not list a corresponding 123xxx type, nor a B18D motor. That's probably a typo.

Same with the P130 F ('66 model year). No 133xxx, no B18D listed -- another typo.

P130 M does list a 133xxx, and A, B and D engine types. Were all the 133s GTs? No telling.

P130 P ('68 model year) lists 133xxx, but no 132xxx and no D engines. It seems the B18B became the standard dual carb motor for that year. Also for the P220 P.

I have heard from several people who I would trust to know that pretty much all the mechanical bits normally found on a GT could be special ordered on the lesser models, but it seems I don't have any documentation that confirms that.