Just went through this as part of an upgrade to CS prop with already-installed GRT EIS4000 and LSE Plasma II+.
The LSE does have an output terminal and LSE sells a LED display with a switch that will display RPM, MP, and timing advance.
If you're using GRT, you can pick up the RPM but will have to snip a couple of components off the board in the GRT unit. Sandy at GRT can email you a diagram. I elected to continue using the pulsed signal from the magneto for tachometer input on the GRT. For MP, you will need the MP transducer and put the output from the transducer to one of the auxiliary inputs on the GRT.