Jon, your rod makes sense. Just found this info:
Yr, engine, pin type, part number, forging number
64-71, 273/318, Floating, 2406785, 1518699
72-73, 318, Floating, 2899495, 2899496
74-86, 318, Pressed, 3751015, 3418645
68-73, 340, Floating, 2899495, 2899496
71-86, 360, Pressed, 3751015, 3418645
So yours is the HD version of the 495. Apparently too, all 318 after 74 had the heavy duyt rod, and that Chrysler started consolidating parts after the 360, probably and sensibly to save costs.
I think with technology now though, a wiser choice would be the new light and strong rods. There are some fantastic prices on name brand I beams -Mancini have some Eagle I beams for under $300 and i bought some SCAT rods recently for a touch over $300. Very light, already weight matched and resized with ARP 2000 bolts, ready to bolt in. You do pay considerably more for H beam though.