I'm currently rebuilding a Pro Tour myself, an '83. Sweet bikes! Mine has Suntour sealed hubs front and rear, so I suspect your bike is not an '83. Check out the date codes on your components and compare them to the ones at the www.vintage-trek.com
site, you should be able to determine the year model if the components are original. T-Mar (bike forum member), on the Classic and Vintage forum, is an expert on Centurion serial numbers and could probably nail it down for you also............Anyway, yeah, going from 126 to 130 on the rear spacing shouldn't be a big problem, you can either squeeze it in each time you install the wheel or you could follow the directions for cold setting on Sheldon Brown's site and spread the rear triangle out to 130mm for easier wheel changes. The big problem might be brake reach, as there isn't much vertical adjustability with the Dia-Compe cantis that are on my bike (maybe yours has different brakes?)............And actually, in just re-reading your post, you wouldn't even need to go to a 130mm hub to go to a seven speed, just pick up a seven speed freewheel and thread it on to your 27's and you're good to go. Might take a little tweaking with the spacing, but it should be very close. There's a seller on ebay that regularly sells beautiful Suntour 7 speed freewheels NOS. Good luck-
Here's a link to a nice page on Sheldon's site that shows catalog pages from Centurion's '84 model lineup, including the Pro Tour. At the bottom of the page there's sheet you can click on that shows detailed specs on the models, including the Pro Tour www.sheldonbrown.com/centurion1984/index.html
I notice the whole lineup used Suzue hubs of one type or another in '84-
Last edited by well biked; 08-19-06 at 08:47 PM.