Well, i think that me and a buddy of mine must be an exception to the 7.5 rule. I have been abusing my 7.5 rear for 9 years now both with a 3.42 gear and now my 3.73 rear. I have been using the Auburn posi unit and nothing else to the rear. I launch at 3400 on the line and jerk the tires off the gound with my Mickey E.T.s and haven't broken it yet. I keep the fluid changed twice ayear and add the posi additive to it and run sythetic fluid. This is behind my 406 sbc with 430hp and 437 trq at the wheels.
Now my buddy in his SS Monte runs a 383 and a stock 7.5 with 4.10 gears and runs his at the track with basically the same setup as me and pulls the tires off the ground about 18 inches and carries them for about 6 ft and he runs in the low 11's and has been abusing that rear end for 3 years with this combo.
I hear this argument all the time and i don't know why people put this rear down so much. I have had great success with it. I am how ever going to a 12 bolt with 33 spline strange axels and a full spool only because i am going to be hitting the rear with a 250 shot of NOS on the line. So, i think that might be to much for the 7.5. Other than that i say go with the 3.42 gears they are perfect for the highway and cruising and an occasional romp at the track.. The rear will last like most have already said stay away from the wheel hop and speed shifting cause that is when the drivetrain takes the most shock. I think it will last for you, good luck. I hope this sheds some light for you.
