I'd just look for a hybrid, though I suppose if you are trying to do this on the cheap a MTB frame is easier to find. Playing around with Sheldon Brown's gear calculator, it looks like if it can take 26x2.35 tires and still have some clearance, 700c x 35 will probably fit. A Schwinn Varsity would fit it with clearance to spare, it normally comes with 27" wheels, and mine is wide enough to fit 26x2.35 tires with fenders. Actually, I'd think most lower end road bikes with 27x1 1/4 tires could fit 700x35 just fine.