Hey all,
The Seawolves of HAL-3 started their renowned service in Southeast Asia with UH-1Bs. By 1969 they received their first UH-1Cs and I believe (I'm doing this from memory now) that by 1971 they had received a number of UH-1M upgrades as well. The B models were certainly in service with them the longest, but the later, more powerful birds were there too. Just depends on the time period you're looking to model.
I for one would love to do a 1972 SEAL Support mission dio, but I'd have to clone myself to get the time to do it. Writing on this forum is the extent of my modelling time now!
Oh well...