Can't be certain, but it's believed all the early brass radiators for the 6 cylinder engines up to about 1981 had the same dimensions and mounting
brackets, so they should probably work.
A/T radiators have an extra transmission cooler side tank incorporated into
the main unit. You can use it for a manual transmission car simply by capping the inlet and outlet hose openings for the tranny fluid. All car bodies should have mounting holes for both m/t and a/t units as the a/t radiator is slightly longer.
Your best option is probably just recoring your old radiator to the better cooling 3 row design. In most instances, you just don't know what you're getting with old used radiators.
72 3.5 CSi
88 M6