1989 Chevy Silverado Engine misses the cuts off

1989 Chevy Silverado V8 Front Wheel Drive Automatic

I have a 5.7L that I have replaced with a second hand engine that I found from a guy who imports parts (Im in Australia) from the US. The engine I installed is out of 94 Truck complete from fan to fly wheel so I had to transfer most parts from one engine to the other.
After transfering all the fitments it started OK. It ran for about 10 minutes then stoped dead no spark and no fuel.
After 4 days found out it was the ignition module replaced it off the 94 truck and checked and reset the timing was running fine good power no hesitation great plenty of grunt.
After about a week it started to kind of miss/cut out occasionally whilst driving and then it would just stop completely. I had good flow out of the injectors when it was running.
This was happening Intermittently and now is getting worse to the stage that I cannot drive it any where.
I have replaced ignition module with a new one but this did no change anything.
I had it running today but will only run for a few seconds now.
I have checked the codes tonight and was getting a 43 code which indicates electronic spark control.
Would this cause the engine to play up like it is or could it be something else.
When it was running better a few days ago I pulled the connector to ESC and it did not change the idle at all as I thought is unusual as this item affects the spark and knock sensor/timing.
Any help would be much apreciated as Im at wts end and there are not many people hear to seek advice.