Welcome to the Stovebolt!
I recognize you from another board where there is only one way to build a rod. I think you'll find here that as long as you're starting with a Chevy/GMC pickup built before 1973 (I think that's the year) you can do with your truck whatever you want.
Be careful as you read the tech articles and look at available kits. Most the hot rod stuff is oriented toward 1/2-ton trucks and may not work for your 3/4-ton. Your '58 is a Task Force truck, and I don't know a lot about those, since mine are all Advance Design trucks ('47 to '55 1st).
You mentioned changing the hub bolt pattern. Are you thinking you don't need the 3/4-ton GVW? I'd suggest putting disk brakes on the front, and replacing the rear axle with one that has modern brakes and a more pleasant gear ratio.
Can you tell us a little more how you what to use the truck? Weight of the load, distances you expect to travel, that sort of thing. It might help sort out the options.
