Originally Posted by j-fire
i talked to VRP about buying their larger 5.4L throttle body, and they said it will not fit.

I believe this to be an oversimplification. The 80mm *could* fit, but would need some custom fabbed parts to make it work, which costs $$$$.
MikeR - what size is the stock TB on C32/SLK32/SRT6? I thought it was 74mm...?
EDIT: nevermind, Josh beat me to it