Help to ID very Strange 426 Wedge Block

GTX JOHN said
It has nothing anywhere on the block except for a R6 cast into it.

Garrett Ellison said
Something I'd read from way back when... During the early days of restrictor plates on super speedways in the early seventies (sometime after the introduction of the Boss 429) it's said that some plate designs worked better with wedge heads, others worked better with Hemi heads. I'm guessing we're looking at a hens teeth early seventies NASCAR wedge block, with the ability of being set up for cross bolt caps. What's stamped on the ID pan at the front of the valley?

There was a catalog in the early 1970s called something like “circuit racing parts”
I believe it had the single 4v intakes and wedge heads as well as other engine, trans, and chassis parts. I’ve seen a photo of a complete nascar wedge headed engine sitting on a cart during a Petty engine swap. I’ve heard they’d qualify with the wedge engine and then race with the hemi. The article said they used 426 hemi blocks! You can definitely see the main cross bolts in the pic.