inline 250 with 373 posi???

[ooimpalaoo]

so i have a 1969 c10 dont know what gears are in it now but when i go up hils i get honked at in the slow lane. my truck has a t5 tranny 235/75r15 not once have i been able to use my fifth gear. i dont even care about that fifth gear i just want to be able to have a little fun in my truck. use the fast lane to go up some hills and honk at other people. lay a patch if thats possible???? 250 inline 2barrel carb long tube headers, so duel exhaust. i was told to put a set of 373 gears in.. i found a 373 posi is that the way i want to go ? or what do i need to do here? thanx for the help yet again. was trying to find a video on youknowwhattube but i couldnt...