If you have twin lehman's you may also have velvet drive CR2's. The starboard transmission reduction assy is geared to rotate in the opposite direction of the engine, thus counter rotating props. The 10-13 units are based on the 71C series.
Many of the AS14-71C main transmission parts are interchangeable with the main exception being the planetary carrier. The clutch packs, pistons, control valve and oil pump are probably identical. Not sure about the drive shaft. I think the early AS14's used bushings, the later 1017 used needle bearings.
A velvet drive rebuild with clutches, o-rings, gaskets, and seals will probably cost $750 each. Replacing bearings would be a major overhaul and would cost substantially more.
If you do have CR2's, note the the output shaft is lower than the input shaft. (drop center) If you replaced them with another type you would have to raise the engine.
My opinion: If you can get the 2 AS14's for $100 or $200 each you can cannibalize them and use the parts to rebuild your CR2's. If they need it. AT $500 ea it would be cheaper to just buy ALTO rebuild kits.