When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My guess is it's 8",but the tape does suck.Put it on mine and it lasted just long enough to dial in my distributer recurve.(Putzed with it about a month.)I also tried the Proform Balancer cover,which lasted about 5 miles due to a clearance problem with my billet pulleys.
My suggestion is to get a sewing tape measure and actually measure the balancer.Whatever you come up with,divide by 10 and scribe a mark on the balancer clockwise from the factory mark.This will be 36 degrees.With the distributer vacuum disconnected,when you rev the engine to 3-4000 this new mark should be at 0 degrees if your timing is set right.