My point is set your timing for wherever you do the most driving. You can use a regular distributor to good effect if you get the curve dialed in for where you do the most driving.

Electronic ignition advance control is a nice-to-have. BUT, having the right Air/Fuel mixture for whatever air conditions you are driving in at the moment is MUCH MORE IMPORTANT.

As I said earlier, if you were running dyno tests at different elevations, then you'd worry about ignition timing much more because you'd be trying to optimize at that particular condition.

But, as you are only driving a car on a road, the altitude's effect on timing has much less to do with the engine's performance than getting the A/F right.

And, if you are going to build a Megasquirt to only run timing, that's a wasted effort.

What do you think the electronic ignition timing control does anyway? It allows you to more easily dial in your curve. I'd be very very surprised if it changed that curve in response to air density.

Just buy the doggone EFI system you like the best and run it.

R.