10.5" Flywheel
Sorry I wasn't able to get back. I was out of commission for the last few days.
Frankly, I'm not sure the Summit offering will work. I checked with Summit Tech and they couldn't tell me if it worked for a '75 trans and bell mated to a stock 273 crank. I called the manufacturer, Zoom Performance, and was able to find out a few things:
It's for an internally balanced engine.
It will fit a '80 to '87 truck application w/ 318.
The two-piece crank seal is proper.
130 tooth is proper.
Diameter (not listed on the Summit page) is 10.5".
The pilot hole is 2.16".
Bolt pattern is 3.437", bolt hole center to center.
The Summit page lists the application for '85 to '91.
At this point, I'd go for it, but until I'm sure I'll wait to order.
Thanks for the lead, inertia. And if the new Summit version doesn't work, I'll be talking to 4 speedin.
GR.