I have had a secret longing to put some gigantic wheels on a longboard for a while now. Either mountain board wheels, or perhaps some of the really large inline skate wheels. Inline wheels have been used for push boards (check out the Shuttle 46) they have very little grip. I am more interested in carving, so this does not seem too useful. Searching on the 'fish I found this post. Not only using mountainboard wheels, and not only mounting the trucks on the top of the deck, but routing out holes for a ... drop-up-through? ... Dig.
Inverted trucks with mountainboard wheels?