Ooo wee! I can't say this has been done in a motorhome, but won't say it cannot.

To start... you don't necessarily NEED the stock instrument cluster from the new vehicles. If you can fab one in your current dash, that'd be cool to see. You'll need the harness for the dash stuff tho. Autometer (and other vendors) sell all electric gauges that'll work with these motors. Easy pickins!

As for the VATS... there's a way around it, as long as you disable it (or have a tuner disable it) within the PCM. Otherwise, you'd have to have the in-dash harness, complete with all stock components (i.e. BCM, etc) to form a closed loop system (unusual & not the best route). VATS can be disabled with tuner software packages like HPTuners, EFILive, etc.

Good luck, ask questions, and posts pics!