The T-37 originated in 1970 1/2 and was continued through the 1971 model year. 3 body styles. 4 dr sedan, 2 dr sedan and 2 dr hardtop. There were about 43,000 or so built in 1971 with 29,000 or so being 2 dr ht's, 9,000 or so being 2 dr sedans and the remainder being 4 dr sedans.
T-37's had rubber mats (carpet was extra), no guages just lights, 6 cyl., 3 speed on column, cloth/vinyl interior, E78X14 bw tires and not much else. It was the base/entry level Pontiac A body.
For 1971 any Pontiac engine was available in the 2 dr sedans and 2 dr ht's.
The GT-37 was an option on any V8 engine in a 2 dr ht T-37. It consisted of Ralley II wheels with no trim ring and raised white letter G70X14 tires, dual exhaust w/GTO exhaust tips that extend through GTO style real valance panel, heavy duty 3 speed with floor shifter by Hurst, hood hold down pins, special badging and special stripes (2 kinds in '71, eyebrow was early and sword stripe was midyear)
You might want to check out the following forum. There are others also.
http://www.performanceyears.com Then go to the forums. Lots of Pontiac specific information there.