The closest Briggs I can find is the 121S02-2005-F1 @ 3100 rpm or 121S12-2008-F1 @ 3800 rpm. The crank on the 121607 Type 0152-A1 is .8735 inch diameter. The length wasn't specified in the crank drawings.
Now the 121S02 and 121S12 crankshafts are .875 inch diameter and the length is spec at 3-5/32 inch. Both these engines have heavy flywheels. So you to ream the pulley center some and may need to shorten the crankshaft some; unless, you the additional clearance.
Now didn't look to see these are fixed speed engine or variable but this should at least give you a start point for your research.
