There have been some frames on EBay (i.e., Cutlass for one) that say they will fit on a Chevelle. Is this correct, and if so are there any more that will fit 67 sb???

A-Body frames will generally interchange from about 1964 to 1972 but certain mounting holes may be different or not there between the body and frame or engine \ trans mount. These you will discover when you go to put the two together.

68 to 72 are extremely different from 64 to 67
and I'm no ace with 64 to 67 but I think there are some differences with these frames also
but as for b o p they are pretty much the same when compared to frames of the same years
even the engine mounts unbolt and the correct holes for the different engine mounts are already there