Earlier this year I did a build because I wanted to, and that was reason enough for me even though I have an EBR. The 1250 by itself isn't going to make allot of power, but as part of a system it does make total sense.
That said I suggest the 1275 kit, more displacement for the same investment, but again as part of a total system approach.
http://www.hammerperf.com/xlbigborekits.shtml This is the package I ordered from Hammer Performance, I have tuned and verified AFR and timing but have not gotten it dynoed for HP/TQ but the improvement is dramatic! Yes, there are "better" ways to go that fast or faster for the money but I like this bike this way.
1275cc cylinders/ pistons
Cometic gasket kit
Crush head porting (7mm valves, 1.900 intake, 1.610 exhaust, conical springs, titanium retainers, 30deg squish band)
605/591 cams (some clearancing was needed for the bearing race but a nice fit)
3/8 hammer pushrods
Throttle body port/match
And the bike already had a Drummer exhaust and K&N filter
@Marc83, I just saw you were in my area, if you want to check out my build I am sure we could meet up sometime.