Rick, if I have this correct, you still have code 29 stored in the soft top controller. You have driven the car, read the codes out twice, attempted to erase, but it is still there. Further, you have confirmed this code by failing to measure AC voltage on socket "9" of the Y-connector while the left front wheel spins at 1 rev/sec.
If the above is correct, then the trouble is somewhere in the ABS or the wiring between the ABS and the soft top controller. This begs the question: is your ABS functioning properly? If it isn't, troubleshooting that problem may be straight-forward and correcting it will probably fix the soft top as well. And if the ABS seems fine...well, it may be considerably more difficult to find a solution.
And hey. Do you mind posting what you paid for this car and how many miles it has? I'm trying to get an idea of how much to ask for my '90 300SL if I decide to sell it.