Dave, the 3.07 has worked very well. In a perfect world a 3.24 would be a bit better as far as fifth gear, however only a tiny bit as you'll see in a moment. If I went to 3.42, I'd have more first gear than needed. How? Well, the T5 I got had first at 4.03, 2nd at 2.37, 3rd at 1.49, 4th at 1.00 and 5th at .86. So, first is 4.03 x 3.07 or an overall at 12.37 (the OEM AD 1st gear ratio was 12.08). With 3.42, my overall ratio in 1st gear would be around 14 and that's not good for driving in a metro area as you barely get across the intersection before you have to shift to 2nd...unless you're using notably larger diameter tires. As for a 3.73 rear end, there was a T5 with a 3.50 first gear but those aren't too easy to find...they were used in early 80s minivans. 3.50 first with 3.73 rear end ratio would be 13 which is workable. But in my case, second and third gears follow very closely the OEM AD overall gear ratios, so driving feels exactly like it did with the original 3 speed and the best part is I'm still able to haul up to 1000 pounds of "stuff" around if necessary. Then when I get to 4th, engine rpms drop by 25% (basically the difference between 3.07 and 4.11) and in 5th, another 14% drop happens. On flat to gently hilly roads, all is well. In more serious hills, I drop down to 4th and then in steep mountains I can still use 3rd just as I would have with the original OEM gear ratios. I should mention the 235 made from 1959 forward used a camshaft which produced more torque at a lower rpm, so it is happier running at 2000 rpm than say the 1956 235 which didn't produce maximum torque until 2400 rpm and will lug more noticeably at 2000 rpm. By 1959 people were becoming more concerned with air pollution (smog, basically) and the 235 was a nice target as the thing was never designed to be a high rpm engine in the first place. The new cam simply increased efficiency (it was in ways a return to the early Corvette cam) and let GM say they were taking steps toward a reduction of fuel during a wide band of use...which is true. If you look at the torque line for the 1959 235 it is interesting. Here:
https://www.gmheritagecenter.com/do...hevrolet-Trucks/1959-Chevrolet-Truck.pdf and go down to page 59. You'll see from just before 1600 rpm to around 2500 it is basically a long and lazy flat line. Lots of nice power for you. Then after 2400 it begins to more sincerely decline and by the time you hit 2700 it is dropping notably. Key point is in fifth gear you get a very long rpm range to enjoy. If you compare it to the torque line for the 1959 283 it is different...the 283 runs up to the high point around 2200 and then starts declining, so there isn't that long flat line of power...more of a short sweet spot you need to hit.
