My clock on an Intermatic T101P3 timer went belly up and I got a new 110V model. However the problem with the new unit is that the output gear location is slightly different relative to the two mounting holes. This means that I can bolt the clock onto the body, the gear doesn't mesh and driver the timer.

Do I have some old unit that new clocks can not be installed onto? Or are there multiple clocks that mount to different timer model?

I brought the old one into my local pool supply but they only have the model that doesn't fit right.

Or I might simlpy figure out a way to jury-rig and mount the new clock by drilling new mount holes in the appropriate location.

They have an "old style" and a "new style" the number on motor tells all.
Hope you didn't throw it out. If that doesn't fit, it is the other, just watch voltage as well.

Actually it turned out to be a newer model, the WG1570-10D. This has the output gear on the correct side. However, the flange on one end was slightly different so that when I installed it back onto the timing switch body, one hole now only lined up with a hole that was untapped. So I took the whole thing out and tapped the hole with 4-40 threads and got it bolted back. Done.