Ok this is what I've got. 1984 C-20 350, 700R4 according to RPO code it has 3.73 gears. This is the semi floating axle. I use this truck to commute to my day job as well as for farm use. Not so much on the farm but for farm runs. Feed, supplies, equipment ect. I have recently purchased a 18' trailer, it is technically an open car hauler, it has custom built short side I will use it mainly for a large utility trailer maybe a few times of year my old Cadillac will get a ride on it. On Saturday I will be headed over the pass with the truck and trailer to pick up a small tractor that weighs in at about 2,000, making the trailer right around 4K gross. My feed runs, I'd like to be able to get 2 tons at time so that would mean the trailer would gross 6K. I know with a 350 I won't be breaking any land speed records, but I'm pretty sure from having run a couple 2K loads on flat land I'm not going to be happy in the pass. So after this Saturday I'll know better how bad it does in the mountains, but I'm debating going either to 4.10 gears or 4.56. Your thoughts?