DIM Electronic Advance Ignition

It sounds like you reproduced the basic functions of the spark system used on GM TBI V-8's ca 1985-1995 (trucks, Camaros, ...), known as the "small cap" or "computer" distributor. Mopar's "no weights, no vacuum" distributors of the same era (K-cars) with "spark control computer" were probably similar, was Ford's TFI system (I think). You will be able to "change weights" and "trim vac advance" from the driver's seat.

You might leverage most components from a GM "8-pin module" and coil. As I understand, it outputs the base timing signal on one wire and your computer returns that signal with spark lead desired (similar to Ford EDIS interface many Megasquirt owners control). I got a junkyard set for all my old Mopars. I will use a Holley Commander 950, which interfaces to the 8-pin module, and acts on a knock signal.

Grab the GM knock sensor (block drain passenger side) and module at the same time. It screwed directly in the block drain of my SB and BB. On my slant, I needed a bushing (3/8 to 1/4 NPT?) for the larger drain. It outputs a single-wire digital signal: high = no knock, low = knocking.