Are you sure that your "barn builder" trans shop used YOUR old trans and not a different one that he had laying around?
Also, i'll just toss this in, may or may not apply. If you USED to have a shift kit in it and he used stock gaskets on a different shift kit seperator plate, it could mess things up. Reason I say this is because when I did a Transgo 1-2 kit on my TH400, it said I HAD to use the Transgo VB
gasket from the plate to the case for it to work correctly. I take that to mean that if I used a stock VB
gasket with that seperator plate, it would NOT work the way Transgo designed it.