What do I have?

I bought a 65 Barraduda that it appears someone was fixing up for a drag car. The guy I bought it from got it from an estate sale. It had set in a garage for about 25 yrs. and he did not have much info. on it other than he was told the entire driveline was from a 74 Duster. I believe this may be true. I know the engine is a 360 it is stamped on the block. Also it has the front disc brakes and calipers from a 74 Duster 360 fit it. It has an Edelbrock intake, Holley carb, and Hedman headers. Looking to see if their were any internal mods, I pulled the timing cover, chain and gears to see if their were any markings on the front of the cam. The only markings on the cam was a U on the front surface. Can anyone tell me if that is of any significance? It also has the numbers 876 on the bottom of the oil pan it looks as if the numbers were welded on. Any significance? The trans is, I am sure a 727 but their is no tag on it. Any way to tell if it would be original to the 74 Duster? or the 65 Barracuda? Last of all it has an 8 1/4" rear with no tag on it. I know it is a posi (it spins both tires) but how do I determine the ratio? If the cam is stock what would be a good choice for street and strip cam?