IMHO...and after approx 300 4L60 trans rebuilds....
You would be better off in the long run to grab a 4l80 E and its original engine, plus all the trans and engine ECU's.
While it is possible to get the early 4l60's to work with later engines, IMHO, its not worth the effort.
I dont build 4l60's anymore, maybe I am just getting old....
Just my 2 cents worth.