Now that I've got it running Fuel and Spark via MS here's an update.
Same 3.0 engine as before (cams, headers) except - deleted AFM (hurrah!), 3" inlet incorporating IAT, cone filter with velocity stack, cold air box, 28.6lb high z injectors.
Megasquirt:
MSnS-E s19 v021 ( I think) Will shortly change to latest recommended.
MT 2.25v326 (I think) WIll shortly go to v514.
12x12 fuel
12x12 spark
via welded spare distributor, using stock distiributor VR sensor, VW coil & ignitor (ex scrap yard).
Once I'd read the MSnS info carefully and did some bench tests the mods required were minimal:
1/ VR sensors send an odd shaped AC signal, use trigger "goes low", ie pretty much the same circuit as the stock v2.2 board.
2/ VR sensor has 2 connections, one (on trailing side) must be grounded otherwise the signal is unreadable. The other conector runs to MS via center of coax cable for sheilding.
3/ I'd previously put a larger 0.01uf cap in C12 to help even out rpm signal from the coil. Had to swap this back to 0.001uf - ie same as stock board otherwise MS couldn't read rpm below 300 - ie couldn't read cranking !
4/ I'd previously put a 1600ohm res in R10, swapped back to 390, now running a 270ohm res here as again the MS couldn't see the weak cranking rpm signal.
5/ Spark signal output via FIDLE jumpered as per standard MSnS recomendations, triggers ignitor by "grounding".
6/ Time based cranking, set to wait 4 triggers.
I roughly copied the stock ditributor advance and vac advance curves into an MS 12x12 map and it STARTED FIRST TIME !
I Quickly adjusted the trigger angle via MS and once that was correct (50) and reverted to my "rough" map it purred ! Rock steady 1000 rpm tickover. Quick test drive reveals all is well, now to fine tune.... where's that dyno !