I Don't really no what a realistic price is because i've never had one that wasn't a direct factory fit so i dont want to say a number too low and scare people off or a number too high and be taken advantage of ya know? but i guess between like 250 and 350 or somewhere around there.
good alts typically dont come cheap, my personal suggestion is call ohio gen and see what one of the denso hairpin alts would run you if it will fit. had one on the tib and loved it. rated at 275 benched 320. thing was a monster.