Looking at the pictures I see that you have a very nice truck! Thanks to your Grandfather and Uncle that have preserved it as well as it is. I grew up on a farm in central North Dakota and understand the way trucks were used/abused too often. That's a very nice old truck you have there. I vote for changing the ring and pinion (theres a good thread here on that) and leave the rest alone. A legacy to your Grandfather, be proud when you drive it!!
I will add, I live in the outskirts of Seattle, I changed the gearing in my truck to 4:11. I can now keep up with traffic. Yes I have to be careful about following distances because the brakes are 70 year old technology. I don't go on the Interstate with my truck stay on the side roads and enjoy! My $.02
If you make a change try to keep the appearance original and
do bolt on items so the truck can always be brought back to original
A good example from Plowboy is to change the ring and pinion gear.
Jeffrey
