You can buy radial tires for your truck just about anywhere.
215/85 R16 tires are the closest radial size to the original tire size. You can still buy radial tires - usually designed for light trucks in R700x16 size.
If you want whitewalls, contact Diamondback Tires.
www.dbtires.com All of their tires are modern radials and the Auburn series are made to look like bias ply tires with a vertical sidewall and a pie crust edge without the radial bulge. I highly recommend them. I have them on multiple vehicles.
If you plan to drive your truck, especially on the freeway, I strongly recommend against trying to reduce the height of the tire by 2 inches. The smaller the diameter of your tires, the slower your truck will go at the same engine speed with larger tires. Your engine will have to work harder (higher rpm) to achieve the same speed it would have with properly sized tires. Considering the top speed of your truck is about 65mph (comfortably), you don't want to reduce that if you don't have to.
Also, it is much easier to drive without power steering when the tires are taller and skinnier rather than shorter or fatter. The steering wheel centers itself easier with taller skinnier tires than with shorter , fatter tires.
I drive my truck like a modern vehicle all the time and have put 10,000+ miles on it in the last 3 years.
Installing the right size rims and tires made a night and day difference in how the truck drives and handles. I regularly drive 55-65 on the freeway.Before and after pics below with fat 15" wheels and tires and correct 16" wheels with larger diameter tires.
