Does anyone know of a double roller chain that will fit under the stock cast alum cover? (Stock cover - $25 on ebay, aftermarket cover $200, I canthink of better ways to spend the dough)

Why not use a ZZ502 Timing Set from GM? Oversized single roller.

http://www.boomspeed.com/mc71454/tgearGM.jpg

I am considering a solid roller which will require pretty heavy springs, and I am not sure if this is going to be too hard on a single chain.
The motor will not be used in a daily driver, but I want it to be as reliable and trouble free as possible for a 650 hp combination.

I see by the pictures of the new 572 on Salee Chevy's website that it uses a stock cover and presumably the ZZ502 kit. The 620 hp street motor has a hydraulic roller cam, which obviously doesn't need the springs that a solid roller does. I see also that the 720 hp race version of this motor uses a solid roller and the appropriate springs, but they don't mention whether or not it uses anything different in the way of the timing chain.

Interesting...I would like to know myself what is in the 720 HP version.

We put a ZZ Chain in Scott Blauuboers Chevelle with his solid roller and he is in the 10's now.

I've been researching this for my buildup. So far, no double roller for MKVI. Check out Cloyes part number 9-3149A ( Hex-a-just); 9-3149 (Original true roller) or C-3213 (heavy duty). :D