The bad on mine is damaged very badly, i do not necessarily need a new tailgate

 

72-74 differ from 75-78 beds. The early beds are longer.

 

so i found that the 72-74 gas cap is on the other side, could i just run lines going across? or would i have to change the sides of the exhaust and gas tank

 

Bed may or may not even fit correctly. 75-78 cabs were a bit longer to the rear so i think the bed was shortened to compensate. This was a member here years back, he had one of the early beds on his truck and it was a 75+ and it fit like this(dont mind the photoshopped wheels)