[special-K]

Hello and welcome to the site. How far along is your truck? I really can't answer you question without seeing pictures first. Didn't you read the rules? Heh heh,just pulling your leg. But,I sure am curious to see what you've got.
You can find the steelies made new from Wheel Vintiques in a variety of sizes,either through them or vendors such as Summit Racing. To figure your back spacing,lay a straight edge across the back of the wheel from bead edge to bead edge and measure down to the surface at the back of the wheel stud holes. I'm not familiar with what an S10 requires,but I know the 1/2t truck wheels generally are about 4" +/-.
There are other sources for custom made wheels but I think you'll find what you need with off the shelf wheels from Wheel Vintiques...and a couple choices in styles,such as good old OEM style and smoothie. Keep us informed which what you end up with. You may have noticed the pre-47 message board runs a bit slower than most others and the more members with these great trucks the better. Glad to see you here and if you get a chance,start a thread to show us what you've got.