Just to throw this out there, I had trouble getting my 23 spline single disc unit to slip in. We blame it on the crank register type of pilot bearing. I put the alignment tool in, tightened everything up, with it still in there, but there was no way the trans was going in (I was working with the engine/trans/k-frame out of the car). Then I remembered an old tip to leave the pressure plate bolts so the disc can move around a little. Boom, went right in.