Overdrive

["Colin Brace (617)726-5085" <BRACEC@A1.MGH.HARVARD.EDU>]

          Has anyone converted a non-overdrive MGB to overdrive? Would 
          appreciate any input. I realize I'll need: a). an overdrive 
          tranny with overdrive, b). overdrive driveshaft is a different 
          part number, so I assume I'll need that. c). The switch is built 
          into the wiper switch (it's a 1974), but I assume I need the 
          Overdrive wiring harness.
          
          Other than that, it seems very straightforward. I saw an 
          overdrive tranny (I also assume all 4 synchro boxes are 
          interchangeable) last year at a meet for $75 (with O/D). I 
          should've grabbed it! How can I tell if a transmission, not in 
          the car, is any good. I realize there is a caveat here, but are 
          there anything I can look for to give me 1/2 a chance?
          
          Thanks!
          
          Colin Brace WA1KWA
          
          BRACEC@A1.MGH.HARVARD.EDU
          
          74 MGB
          73 BMW 3.0s
          89 SAAB 9000S
          81 F-100 (!)