Hi Luc,
I'm happy to hear that the engine worked out well for you. If you need a 4.2L let me know. I have a few I need to move out of here!
As far as the hub adapter, I never looked into swapping wheels so I can't help you. I do seem to remember someone one Ebay selling hub adapters for Momo wheels awhile back. You might want to do a search there.
Cheers,
Paul