eldorado 1985 engine swap?

Hi
I own an Eldorado 1985 Biarizt, car in great shape BUT:
The beloved 4.1 is overheat, any body surprise!!!
My question is ;

Replace that engine with a 4.1 rebuilt Or
a rebuilt 4.5 ?

I know that the same block will fit like a glove, but is that compatible with my ecu, and wiring?

Any body try that?

Looking for advise