Kyosho Ultima Sideways, still basically an Ultima?
 

.....with different wheels, body, top deck and shocks?

I may have one coming and I'd be interested in turning into a Mk1 Ultima.

Feasible?

Cheers!

I think it might be closer to the turbo ultima

Its a mk1 ultima appart from rubbish plastic shocks, body and wheels.

If you found a body & roll cage and put some buggy wheels on it, its 95% a Ultima mk1.