based on the positioning of the motor in that car you should be able to put the traxxas motor in there with little to no modification. What you will need to get is the carbon fiber upper raido tray (if you can still find on) and the rear chassis/gear brace. They can be purchased here:
Throw in a Traxxas manifold
and a pipe
and you're good to go.
I doubt that HPI still has this linkage kit
but here's a picture of how it should look: