it appears to be a heavily modified HPI nitro rs4 2, between the rs4-1 and the rs4-2 the main reason i say that is the chassis being purple, the rs4-1 typically was not anodized purple, that said, the were interchangable.
everything else that would indicate whether it was an rs4-1 or rs4-2 have been replaced. and everything that would indicate it being a "racer" variant of either are also replaced.
it also appears to have a HPI .25, with a big block conversion. i am unfamiliar with that version though, could be New Era possibly? or GH?
very nice find.