Michael,
If your crankshaft has 3/16" x 1/2" rollers, it has already been reconditioned/modified. The T35/Mark series engines all had 2 rows of 1/4" x 1/4" rollers (but in various designs of cage). The 3/16" x 1/2" rollers were used by firms like Alpha Bearings in their reconditioned crankshafts (these rollers are the same as used in the Dragonfly cranks) (but in a different dia cage). If you look at your con-rods, you will probably find that they have thin liners pressed into the big-end eyes - this is the weak point with the reconditioned cranks - the machining of the con-rods (to accept the liners) is often poorly done, allowing the liners to flex under load, and start cracking. Attached is a photo to illustrate the poor machining of the con-rods - being machined, rather than ground, the bores were also barrel shaped.
Hope this is of some help,
Regards,
Eddie.