Scott,
It turns out the 261 rods aren't around the shop. I'll keep looking.

I weighed the stock 302 GMC piston and pin.

Piston: 917.4 grams.
Pin: 219.4 grams.
Total: 1136.8 total. (2 pounds,8.1 ounces)

No wonder the stock engine didn't like high rpm.

Ron