ECM question

I have an 85 s-10 with a tired and worn out 4 banger and 4 speed.
I also have an 89 s-10, with a mangled & rusted body, but with a good 4.3 v-6
My plan is to take the wiring harness and engine out of the 89, and put it in the 85,backed by a 5 speed I got from the junkyard. What I'm not sure of is, the 89 had a 4L60E in it, & I understand it is an electronically controlled transmission, and the PROM is programmed for that engine and transmission.

Will this screw with the ECM by having a different transmission than it was programmed for, or would it still run the engine okay?

Any help will be greatly appreciated.

Adam:confused: