Chris,
You need the shorter upper wishbones, the existing lower Race Runner Evo 2 wishbones can be used if you remove the black plastic spacer and use a shorter bolt for the red plastic rose joint to screw onto.
The Rally car (and Pre Evo) also used shorter dogbones/driveshafts.
There were no issues with the clearance on the roll cage or the Samba pipe.
The MCD Subaru Imprezza and Peugeot 206 bodyshells were a perfect fit on the converted Race Runner. I have not seen an MCD Rally car with a Renault bodyshell, however it is designed for a similar wheelbase and the UK importer had suggested it as an alternative to the MCD bodyshells.
I would recommend you think of an alternative way of securing a foam bumper to the front, I had problems where the bumper would try and tuck itself under the chassis and drag along the ground. Not very clever during a race!!!
With the bodyshell, the conversion might well cost more than $500. Have you thought about spending slightly more on the Redcat Rally car?
I only converted my Pre Evo Race Runner because I found a used bodyshell for peanuts on ebay. I eventually purchased a Rally car for racing and the Pre Evo is still going strong 3 years later having finally been converted to Evo 3 spec.
Clive