Joined: Nov 2006
Posts: 19,810
Likes: 597
From: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
If you want to stay Raleigh, I don't think there's much difference between Sprite, Record, and Grand Prix frames; Grand Prix has fancier lugs and wrapped seat stays (purely decorative), Sprite has fenders and (sometimes) chain guard; all were made in 25" but who knows which you'll find first. Certainly a higher end model would be nice if that turns up first.
I built a 5 speed around a Lambert frame, with "almost matching" Free Spirit fenders, which came out quite nicely. Really, any frame with horizontal dropouts should be fine.
Are you going to keep the 2 cog thing? I'm going to be trying that myself pretty soon.