Transmission question

[MowerModder]

I've come across a great source of tractor parts near my house.  There are at least a dozen transaxles laying around.  Some of them on the machines, some of them sitting on the ground.  The guy wants $50 each.  Wheels and tires included.  I think that's a damn fine deal. 

Anyway,  I have a bunch to choose from.  One in particular caught my eye.  It's a Peerless MST 206 502A.  I know nothing about the MST models.  Are they any good?  Are they similar to other Peerless models? 

I've also got a line on a peerless 600 as well. 

In general, what seems to be the preferred/most popular tranny for All Terrain Mowers?

MM