I don't think the mods have to be done, at least on B & E's. The tunnel shouldn't have to be cut. Upon viewing the TKX case, it is somewhat more rounded on the top of the case. The TKO has a shifting fork inspection cover on top the transmission case cover that is tall enough that it requires the transmission tunnel to be cut and have a piece of sheetmetal welded to the tunnel. The TKX has a one piece case, no cover on top, so it is lower sitting in the tunnel.

It also looks like TKX has more shifter locations , at least fore and aft, so that it can accomadate the different locations the shifter hole is in between the different models. It may be in the middle and not slightly offset to the driver's side like A833 and SST/Keisler shifter locations though.

I called and inquired about what it would take to put my TKO Perfect fit kit into a different car, specifically a big block, and was told that they were specifically fitted to a certain model. I couldn't put the kit in say, an A-body or B-body, but if I wanted to put it in another E-body with a big block the only thing I would need would be a bellhousing. The crossmember and throwout bearing is the same. I am guessing this is because Keisler modifies the TKO case and the shifter turret location specific to each bodystyle. I think that the TKX would fit easier across the board and not HAVE to have modification to it's case or the car that is recieving it.