Hey,
I had several of yall inquire about the L28 bell housing dimensions to aid in designing of other transmission adapters. Here are the deminsions that I used to make my adapter for the L28 side. These measurements were taken by CMM from a Nissan 5 spd transmission bell housing, so they are as accurate as the factory castings can be. All the points are referenced from the center of the input shaft bearing bore. I have found the dimensions to work VERY well with my adapters.
I would ask that if you use these dimensions to make any parts other then for yourself that you donate some money to the site.
This is the bolts, dowel pin, and starter location looking at the engine from the rear: