converter question

I'am putting a 727 transmission in my Duster in place of the old 904. It has a mild 360(9 to 1 comp. magnum heads, 230 duration 470 lift cam, air gap intake and tti headers and 2.5 x-pipe exhaust) and 3.23 rear. I bought an 11" B&M Converter from my buddy and now he can't remember if it stalled at 2000, 2400, or 3000 rpm. There are no part numbers anywhere on it. The car is just a fun cruiser and rarely at the track. Is there any way to tell which stall it is other than installing it and test driving? And what effect on driving and mileage would be expected if it is the highest stall version?
Bob