3116 head swap 3126, c7

Tried search and came up short....

These 3116 engines seem plentiful to say the least, and its its looking like i will soon be wrenching on them too, so i want to ask

What is the compatibility of the later engines (3126 and c7) heads with the 3116 block?
My reading leads me to believe that fuel injection system, valvetrain and Other systems were heavily changed, but arent all these engines based on the original 3116 block? I dont have any to play with or check so if someone knows please post your findings!

The HEUI high pressure engine oil is pumped thru a gallery in the head to supply the injectors. The 3116 MUI engine does not use this so I would say the two heads are not interchangeable. Dont know if they changed the injector cup and fuel gallery design either, but they did reverse the flow 3116 is back to front with pressure reg on top of governor. 3126 is front to rear with fuel pressure reg on the back of the head...

^^ correct. Plus using the 3126B head you would need to change the pistons in the 3116 I believe or else they will not be happy banging together. The mui uses different sleeves than a huei

Thanks for the help