Help ..904 has died 4 times !

I sure hope someone can offer some insight with this problem.
I put a 1975-360 from an rv into my sons car with the 1968 -904 from the original 273 engine . i used the special flexplate for the 360 app and a lokar kickdown cable for the throttle valve.
since then the forward clutch hub has welded up 4 times leaving us with only reverse gear. twice the tranny was built by a friend of a friend that suposedly built trannys for 20 years and talked a good game. i bought the oh kits and convertors myself and each time it lasted about 100-200 miles before it died. Next i took it to the local aamco dealer for a rebuild again it lasted 140 miles , now the trans shop working under warranty is telling me the trans should have never been behind that engine , the tranny had the wrong output shaft ( coarse thead nut vs fine thread nut) without enough spline in the hub it was stripping the male splines off of the shaft. then it had the wrong input shaft and the convertor didnt fit right against the front pump , also the pilot of the convertor didnt fit the crankshaft correctly, they changed the convertor to fit the 360 crank pilot hole and now the new nippendenso mini starter i just bought doesn't touch the ring gear to start the motor. I an so confused by all the stories aamco has told me I don't know what to believe . it has been over 3 weeks since i took the car back the second time and i'm wondering if i'm ever going to see it again. every day i call i'm told they're trying to straighted this mess out. I know i have read of others using a 904 behind a 360 , but i'm not having any success with this combo. can anyone offer any suggestions that i can offer to aamco ? personally i'm not a transmission mechanic so i feel frustrated not knowing what the real issue is. Thanks