They will take a 1.75 with no probs, not sure though if they would be era correct, I think 1.5's came onto the market around late 85. They will look OK, it is very hard to tell the difference unless put alongside a 1.75 as it's only a quarter of an inch difference. The 1.75's do come up from time to time so unless you are in a real hurry to get it built I'd hold on for a set of those.
Marty