I have a 68 rivi, I want it to incrrease hp, what it the best carb and manifold for this application

Slap on a factory dual quad set up - nothing like it all eight barrells roaring on a Nailhead!!!! smile.gif

Depends on which engine you've got. Check out TA Performance for what's available, although I'm fairly sure that there wasn't a factory 2x4 setup in '68
Best of luck
Malc

Yep, no factory 2x4's in a 68 Riviera and no Nailhead motors either.