3:54 Gears and Tire Size

My '77 304 T150 3-speed has 3:54 gears and 30 x 9.5 x 15 all-terrains. I use it primarily as a street rig and occassional easy trails. I'm satisfied with the performance as currently set up, but I'd like to increase the tire size to at least 31 x 10.50, if I can do so without turning the thing into a dog at the low end. If I need to have it re-geared, I'd probably put 4:10's in it, lift it, and put 33's on it, but I'd like to forego all of that expense and try the 31's for awhile.

I have looked at all the rpm charts, and I know with 3:54's and 31's it would fall in the "fuel economy" range as far as use of the motor's power band (it already falls within that range with the 30's). However, what I'm looking for is real-life descriptions of experiences with 3:54 gears and larger than stock tires; e.g, "I did it and hated it"; or "you can't tell any seat of the pants difference between the 30's and 31's", etc. Thanks for any help.

 

If you're happy with the way it performs now, going to 31X10.50's won't make any difference.

 

x2, not a big difference between 31's and 30's.

 

Goes like the diameter of the tire ... 31/30 is about a 3% difference. Likely you won't notice it.

 

I ran a 304/T-150 with 3.54 gears with 31's in my '77 , did fantastic. If you had a 4 cylinder, I'd say youd have problems (but if it was a stock 4-banger it'd have 4.10's) but with the 304 the 31's will do fine.