I hate to throw rocks/stones/whatever, but MOST machinists know this kinda stuff 'off the top of their head'. (at least mine does).
2 years ago when we threw together the 357, we shaved/planed/cut the hell outa everything.
My machinist, (Larry Seitlitz/Pro Machine), literally bounced the numbers in his head as we're trial fitting everything. Needless to say, everything fit beautifully the first time..........Maybe I got lucky with my machinist.......then again, he does like 90% performance work.......?