The 2500 RPM won't be a problem for your 235, but this combination of gears will net about 2.59 final drive ratio in OD 5th. You will be down shifting quite a bit. If you could actually pull 82 mph with a stock 235, I'd be REAL surprised. Scared too, with stock brakes & suspension! A 3.73 or 3.90 rear would be my choice here, and give better acceleration around town.
The factory geared the '55 trucks with 1st gear about 3:1, optimum with the 3.90 rear. You'll lose some punch by going to 3.55. With the OD 5th, you really don't need that much reduction. Of course a 4.03 1st gear S10 T5 will restore the initial gearing, but that's a real wide ratio tranny and it's entirely possible the shift to 5th gear would cause the motor to just go flat, i.e, drop RPM but gain no speed. Even if not, I still think 2.59 is too tall for a stock 235 to pull comfortably.
