I know this is a popular question but here goes.

Recommended plug for the following:

JC Performance BBC - 454 bored over to I believe a 468
Hydrualic cam with iron dart heads, 9.35:1, roughly 550 hp, w/850 Demon carb, and Crane Hi-6 igniton. Stock distrib/cap

It's had NGK BKR7E's and V-Power R5672A-8's

Thanks!

I had your combination for years...your NGK 8's are the right heat range.

Try and find the champions with the short ground stap for your application. Very good plug we use them racing. Cup guys use them. There is some engineering behind them.

Are the Dart heads the ones that are like the Vortec heads? (for the spark plug holes anyway?)
Reason I ask is the Vortec heads need the long tapered thread plug with the long protruding electrode. (I think it's the NGK BP5ES or something)

Best to check and be sure, but Ben's right, the NGK 8s are in the right heat range, just make sure you get the right electrode length.

Good Luck!