There are 5 to 6 lug adapters. They will alter the scrub radius, and can potentially cause additional wear to the bearings and balljoints. As far as tires, you're looking at perhaps a6 or 7 inch wide tire at the most that will safely work with the rather narrow stock wheels. In a modern tire size, 215 or 225 on the section width. A better route might be to look for a similar styled aftermarket wheel, perhaps from Wheel Vintiques or Early Wheel Company, that is made to fit you new bolt pattern. You can also get a wider wheel if you're wanting a wider tire. You'll want the wheel width bead to bead to be roughly 2" narrower than the section width of the tire.

Bill Burmeister