It appears you guys are correct & I am wrong on the 7.1" rod. I just called Diamond & Randy said they couldn't fit the ring stack in that C.H. I was getting my info from an old High Performance Mopar magazine article (July 2000, P.53) written by Frank Licari. He goes on about the 7.1 rod (#CRS7100C3D) & a dished Diamond 2618 piston w/ .990" pin. Said it gave a rod angle of 1.82 on the 3.90" stroke.
Years ago I was ordering a set of pistons from Diamond for my 470. I mentioned I intended to add a small nitrous kit, & they talked me into using a 6.7 rod so they could move the ring stack down out of the heat. My pins are into the oil ring grooves using bridges.
Now I'm really confused. May be one of those articles where the motor was never really put together. I know there have been several articles written by a local machinist & our local GM parts dept. about wild Chevy combinations, complete with pictures, that never were assembled. Sold lots of parts, though.