Hy JRMunn, unfortunately wheels and tires are a large area of possible problems. Wheels with multiple different offsets are made that will "bolt" on to a given vehicle, you have already discovered a problem with incorrect wheels on your front axle. Since your truck left the factory forty-five years ago who knows how many tires and wheels have been swapped onto it. The truck would have left the factory with a maximum of two different size wheels, the wheels for the front axle would be the same, and the wheels for the rear axle would be the same, possibly all the wheels would be the same. The trucks G.V.W. would be dependent on what size tires it had, quite often the tires on the front axle are smaller than the ones on the rear axle. My advice to you would be to take inventory of the wheels on your truck, find out how many different wheels you have, then figure out how many are either 6.5" wide or 7.0" wide, you may even find wheels on the truck that would be better mounted on the front axle (for clearance purposes). You may end up having to replace some of your wheels to try and standardize what you have. Quite often wheels and tires are the largest expense when restoring a "Big Bolt", there are many choices, radials vs bias ply, tubeless vs tube type. Finding a shop willing to work on multi-piece wheels is another issue, you won't know if a given wheel is serviceable for re-use until all the components of that wheel have been dis-assembled, cleaned and inspected. There is a lot to think about in regards to wheels and tires for a "Big Bolt", and a good experienced tireman/shop can be of invaluable assistance in helping you navigate the maze that is the subject of wheels and tires for a "Big Bolt", hope that helps.
