I just got a 71 SB last night, and the shift coupler was trashed. I replaced that, did my best with the carburetor, and it runs. But I can't for the life of me find 3rd gear. or 4th. 1st to 2nd is easy, 2nd to 1st is tricky, and 3rd an d 4th are just...non existent. reverse is easy

Are these trannies usually this loose? I can wriggle the shifter around in gear, as though i'm in neutral. This doesn't seem right, to me. I'm suspecting bushings. Where would I be able to buy replacement bushings, and how much are they? Could there be another problem??
Thanks