I think Ed answered this earlier in this thread, you need to look for 22.5's off of a mid/late 50's GM truck. They will look just like your existing wheels. Chevrolet introduce the tubeless wheels on their trucks in 1956. The 5/10 lug pattern you have was only used on the 1-1/2 ton trucks, the 2-ton had 6-lug. With that said your center hole is smaller, so using the later wheels will require a custom made center hole spacer ring.
$1600 sounds fair to me...are you putting traction tires on the rear or just a hi-way tread?
As for more HP, how much more HP are you thinking about? You might want to figure that out before you buy your tires...putting 8.25x20's on the back will give you a little more road speed (they are taller than the 750x20's).
Mike B
