Pulled the plug wires sequentially, but couldn't get the boot far enough away to prevent arcing to the plug (deep well plugs and a harness that doesn't favor removing one plug at the time). Did listen to the injectors with a stethoscope and all seemed to be clicking away - but we did have the connectors off during the engine removal.
Did a compression check and found one cylinder down 10psi, but all cylinders were at the bottom of the acceptable range (poo!). The mystery is that the car seemed to be running OK when the transmission case cracked, so it is hopefully something simple like a cracked distributor or bad plug wire.
Using a timing light I did verify ignition on each cylinder individually.
Just need more time and inspiration.
I need to determine whether or not to keep spending time and money on this rally-x car or just cut my losses. If we are going to run it, we need to weld up the leaks in the exhaust to quieten it a lot.
Charlie G