I am about to obtai8ne a 86 ford F-250 with a 5.0 eng. and 4 speed manual trans. I was hoping that some one could give me some input on it such as what troubles i can expect, gas millage, fule tank size, ect

20 gallon i have a 85 f250 but i have a 351w in it no problems but first and reverse went out but i beat the shit out of my truck and it has like 400000 miles on it