modding 77 gas filler to newer 81-87 style

[gramps77]

So I just cut out left and right refuel areas from an 86 3-4 inches all the way around. Dont worry, that bed had been rearended so I didnt cut up a perfectly good bed.
Can someone give me the measurments for where the top corners of the doors should start from the top of the bed?
It'll be nice to not get gas everywhere when I refuel here in Cali with those stupid nozzles. Then, on to a repaint.