Hey;
I just purchased a 78 T/A with the same 400 4spd setup. It sounds like they needed identical work including the floor, interior, one quarter, etc. Mine was in great running condition though with a lot of performance upgrades and a freshly rebuilt engine and tranny, matching numbers(receipts included). Mine came with t-tops, power windows, locks and all the gauges worked. I paid 5k for it which I felt was a good deal considering having the engine and tranny rebuilt would cost 3k done right. This should give you an idea what kind of offer to make. Also, I bought mine off ebay, not some farm where it was sitting behind a barn for a 2 decades, so it had exposure with lots of interest.