I have a 25" Bridgestone 400 ('84 or '85) that I intend to convert. I've measured and it for sure has clearance for 42's, and may even be able to squeeze in larger (with no fenders). Bottom bracket drop isn't ideal, as it originally had 27" wheels (I want to say it's around 270mm to the ground with 27x1 1/4 paselas). With the 27" wheels I have on their now brakes with 49mm reach just reach. So, 23mm more reach only puts it at 72mm reach for the brakes.