I'm just getting started on a 66 Burb. No power steering will probably dictate narrow rims and tires for now. Big wide tires look neat but they are very hard to drive with no PS. And hotrod or stock?
My original rim size is 15x5.5 inch with a 6.70x15 tire. Backspacing is another issue that you need to look at. Mine was 3.75 inches.
Yours being earlier yet, will be even narrower.
Someone will pop in in a bit with some good recommendations. Someone gave me this website. Good info.
https://www.rsracing.com/tech-wheel.html