The donor 66 Falcon I scored the other day came with a top loader from a 69 Mustang 390 ci, as I could decode by "RUG M3". Might be wrong tho. But my concern is the 302. The casting numbers behind the starter motor are the following; "E0AE D3C". Is it a 1980 engine from a full size car, or a 1980 casting, used in a later year? I understand the HP rating is kinda low for this years, but which was exactly the HP? The cylinder heads have like a by pass pipe, connected from the rear end of the each head. What is it? Is it necessary? Thanks in advance for your help.