I believe this is a 2500 chevy truck. If I am not correct, let me know.
If there is no spark, I have a feeling it is the ground wire for the coils. There is one common ground that all coils are spliced into. The wire should be grounded on the driver's side of the engine toward the front, on the engine block. This is a common problem when spark is lost. The wire will be black in color and it goes to an eyelet type connector that then bolts to the block.
Now, there is a chance it wasn't connected when you replaced the engine or was damaged. I don't know if you are using the same coils or what was done. But, when you locate the ground, if it is connected don't assume it is good. They corrode, come loose at the crimp, and so on. The easiest way to check is by simply running a new ground to the wire itself and see if you get spark.
Let me know what you find. Also, I said the ground was toward the front of the engine block, driver's side. I am saying that from memory. It could be further back on the block, but it is on the left side.
Friday, April 3rd, 2020 AT 5:57 PM