I started with just the ignition to keep things simple.
A VR distributor was built to use as a trigger. Read the manual how to configure your board for the type of ignition trigger you use. It might be a chance to solder in a few leads, or move a few jumper pins.
What did I learn?
1: Not all boards have a Q16 transistor installed to use as a coil trigger. DIY autotune can sell you one.
2: Even on the 3.57 boards you may have to take it out of the case & solder jumper wires on the back.
3: If the stimulator works but the car doesn't, you may have to twiddle in the variable resistors on the circuit board. ( hysteresis in particular )
4: Now you may find the stim doesn't work. You will have to twiddle them back. ( Easy to forget. Why doesn't my stim work ? It worked yesterday....)
5: The trigger wires from the distributor need to be shielded and away from plug & coil leads or you will get mystery trigggering. Read that again. It's really important.
6: Oscilloscopes are getting cheap on eBay. The Hitachi V212 is a fantastic tool for framing a Megasquirt question. I got one for $60 including shipping. Even if you don't know how to use one they are intuitive. being able to compare two different signals visually can really help to locate problems.
How does it run on ignition only ?
Great. maybe it's better dwell control or a better advance map, but it starts faster & seems noticeably smoother than with a well tuned points set up. ( using the same coil, leads, & plugs.)
I also grabbed an Idle air control 4 wire stepper motor & I have tried it with a stim. It works great on the bench. Imagine smooth idle at cold start ...
Off to build the injector bungs...