Give this guy a call. He should be able to ship you a pumpkin for far less money.
Tom Myers, Miami, OK 918-542-3871
Original tires should have been 7.00-15, iirc. When I put 16" wheels on my truck, I went to a 7.50R16, that kept the tire halfway narrow, but upped the diameter to 32+ inches. My spedo reads 7% slow, but you won't be in any races. The thing to do is to get your differential in and tire situation resolved, then get the proper speedo gear.
One thing to be careful of with the wheels is the setback, distance from the back edge of the rim to the hub mounting surface. You can run into clearance problems with the tie rod ends on the front if your setback is deeper with the new wheels. My 16" Chevy wheels are almost 2" deeper, so I am still running 15's on the front, I will have to make spacers to run the 16's. And don't forget the radials will be wider, too.
Take those rusty rims to the scrapper, they're dangerous.
