Overdrive or Gears

[f.monroe]

I have been driving my 87 3/4 ton a lot lately . It has a factory 4.10 posi rear axle and the little 350 is wound pretty tight at highway speed . (My 05 work truck has a 4.10 rear and turns about 3300 in drive and 2500 in OD . I figure the final drive is around 3.0x with the OD . )I thought of an overdrive 4L80 but have been thinking 3.42 gears would help and is a lot cheaper . I think the 3.42's would still allow it to pull and with the 33x12.50x16.5's would offer a little releif on the highway . What do you think ? 3.42's or a 4L80 ? Also , has anyone here installed a 4L80 in one of these trucks and did you have any problems ? Frank