It sounds like you are very lucky to have found a couple of old trucks that have not been messed with. The old Chevys did an astounding amount of work with 216s and 235s. The 261 was a total work horse. That said they did it with torque and gears. I'm sure you can get more out of it but it is what it is. Many old trucks that size had 5 speed trannys with 5th gear being overdrive and some had 2 speed axles. If yours doesn't have those it might be something to think about.
On the Dodge I'd change the rear end gears. maybe 3.55 or so. Depending on tire size that would get you around 60 mph at 3,000 rpm. It would still have plenty of power for regular 3/4 ton pickup work. Dodge also made some trucks with 5th gear OD transmissions. My dad was a MOPAR flathead six guy we had a lot of them through the mid 60s. We moved from Texas to California in a '52 Dodge 1/2 ton 3 on the tree pulling the biggest Yuall-Haul they had. A little slow up some of the mountain passes.
