Tires/Gears/Power/Drive Quality, mpg, anyone...??

[ISDE rider]

I have been trying to work out tire and gear choice. Someone must have experience with size, drive quality, etc....
My 70 Travelette has 4.10s and the T34OD trans w/392. I have been through 265/75 16, 255/85 16, 33 12.50 16.5 and 35 12.50 16.5 tires. With the 265/75s towing and drive quality are great but the trans feels close ratio except the huge gap between 3rd and 4th. The 255/85s lost drive quality and gearing was only slightly "better". The 33 12.50s were junk when they were new so tough call there. The 35s seem to make gearing great for the highway if your not towing anything heavy. With four guys and a huge box trailer at 6ooo# it was a lot of work and OD was out of the question with a strong headwind. I am still working on mpg considerations but it looks to be suprisingly close, 11-13 not towing and 8-10 or less towing depending on load and conditions.
The Question; How would 265/75s and 3.73s compair? Gearing is about the same but how much do the huge tires effect performance?

Looking forward to the usual wealth of knowledge shared on this sight.

Thank you in advance for your time and consideration.