You almost got it. Interestingly, the hull # on my H37C is also 308 so:
HUN37308M83A = Hunter 37, Hull 308, Model Year 1983, Production Month A or August. Back when Hunter built our boats, the new model year started in August, I guess so they would have the new models available to sell for the winter boat show season. Ergo, my boat was a 1983 model built in August 1982. The month codes are:
A-August, B-September, C-October, D-November, E-December, F-January, G-February, H-March, I-April, J-May, K-June & L-July. Your boat is Hunter 33 #308, a 1980 model built in February 1980.