I'm guessing this has been asked before, however I cannot find the answer.

I am swapping a 4.8 and 4L60E into my 2.8 MPFI 700R4 Firebird. My question concerns the mechanical speedometer I have. When I do this conversion, I want to keep the mechanical speedometer as the conversion to electronic is daunting. I have read that there is a converter for the 4L60E to make it work with the mechanical speedo, however my question is will it send the necessary information to the engine still?