Look out for the chain line / belt line. With a chain, you don't have to care about this much as a chain will run at quite an angle without problems (derailleurs rely on this, obviously.)
The belt will be much less tolerant of a chain line that is not straight. With the pre-centertrack belts the alignment between front and rear sprockets needs to be within +/- 1/8" otherwise the belt is just going to run off of the sprockets. Centertrack prevents the belt running off, but I doubt it will run great if the sprockets are misaligned.
Worth googling for this - you'll find many conversion projects that went off the rails because of this. One challenge you may well run into is that even if you are able to get a combo of BB and crank that will allow the belt to line up, the chainstay will be in the way. I have a Civia Bryant and the drive-side chainstay is shaped so that the front sprocket will clear it - i.e it has a "dent" in the chainstay. This suggests that it's hard to have a non-dented chainstay design that will work, and, well... most chainstays don't have dents.
On balance, I think you'd have to be really attached to that frame.
One other thing to verify is the range of spacing you will have available between the front and rear sprockets, and whether this will be compatible with the combinations of belt length and sprocket sizes available. You need enough range to both be able to get the belt on, and to tension it properly. The information about the ranges needed for various belt/sprocket combinations is available on Gates website.