Pinion angle and driveshaft length.

If the perches aren't welded in place simply point the pin at 0 for now and measure for length.
After the shaft is installed then correct the angle to oppose the shafts angle, and adjust the angle so that it is at 0.0 with the shaft under load and nothing else.

The length isn't going to change much to have any negative effect on SY engagement.

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