Where to start?
You can keep 8 lugs if you want. There are several suitable 3/4 and 1 ton rear axles out there with better gear ratios available.
Here's a long and drawn out thread (with bad picture links..) about swapping in a GM 14 bolt rear. I think this is the most reasonable swap for an AD 1 ton truck.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=599879Also as mentioned you can, if you hunt long enough, find 4.10 gears for the old Eaton axle.
What OD transmission to use? There are a few to chose from, the T5 is an easy swap but not very stout for a real working 1 ton, better off in a 1/2 ton. Then for a working truck the NV4500 is a good swap with a little more work. Lots of threads about both here if you look a little.
What gears or OD do you need to go the speed you want? Not sure you even asked but you should find out first before doing anything.
http://www.onlineconversion.com/bigger_tires.htmThen the next question is are the brakes up to the task with such a higher speed? After that can you even use that speed on anything but a downhill with the current engine, do you have enough power to move the truck through the wind? All things to consider.
Driveshaft. It is made in two pieces because it needs to be to stay straight. If you want a driveshaft that looks more like a banana replace the working two piece shaft with one long slender shaft... Here's the explanation in these manuals
http://www.stovebolt.com/techtips/driveline/setup/index.htmlGrigg
