Engine cuts out when warm efi 3.9 v8

Hi looking to see if anyone can help. I have a landrover with rangy 3.9 efi v8, Mallory coil dizy and module, it runs on lpg and petrol. The fault is same on either fuel. I have swopped the coil over with a knowngood one and fault persists. The fault... The engine runs for about 8 miles or after 10 mins tick over and then cuts out... No spark after two hours it restarts. When it fails I have removed fuel rail and temp sensor wires and it still does not run. Has anyone any idea what the fault is?

I know nothing about the Mallory stuff & I'm inclined to think the normal LR tests wouldn't be applicable. This might be worth a read: https://www.pistonheads.com/gassing/topic.asp?t=457775

ignition amp if you have no spark when its hot