Yes, as you say, the '82 had Gran Compe 450 center pull brakes; but are you sure they were brazed on? (I rather doubt they were, but what do I know). And for that matter, do you know if a cable stop was brazed to the stays? The catalog is unclear on this, but the photo suggests the stop was brazed on.

The 1982 brochure does show, however that the 720 was available as a bare frame, and does not indicate that the bare frame differed in any way from that if the complete bike.

I ask because I have a 720, that I bought new, as a bare frame, in the spring of '83. It was made, according to the serial number, in late '82. It has none of the brazed-on doodahs I ask about, and it is not even clear what wheel size and what brakes the designers intended.

My frame has an integeral seat post pinch bolt, which makes it difficult to install a separate stop for the center pull brake. So I rather wish I knew what the boys at Trek were thinking.