I don't have a catalog from the 70s.
Dougs had a header for the early A's - its three for four pieces - and won't fit with a 727.
About 10 +years ago they redsigned it to maybe 2 pieces each side? The TTI came out with their version.
Anyway - A long rambling way for saying I don't know if their B-body also fit some 2nd gen A-bodies.
Nothing wrong with 2.5" collector for most engines people are using on the street, or street strip. In fact its probably better than 3" until the engine is up around 6000 rpm.