TO bearing question

[69importkilla]

So I am looking at a hydraulic TO for my D&D T-56. A couple of places have TO bearings in the low $400 range for this application. If this tranny is supposed to act like a Muncie, why cant I go with one of the $150 units listed thru some of the major mail order shops? Is there something special about the "conversion" bearings they are offering at $400? I'm doing this on the cheap so this is important..