Help to ID very Strange 426 Wedge Block

I found this fresh 426 Standard Bore block in my late
friends Shop (Tri City Perf) along with a bunch of regular
426 blocks. Greg (RIP) was a top Max wedge engine builder
and racer for decades.

It has provisions for 4 bolt mains but does not have them.

It has a lot of support ribbing that I have never seen on any
block in 60 years. I have seen a lot including Marine/Industrial/Race
blocks but nothing quite like this!

It is very heavy compared to my other blocks and very beefy!!

Perhaps aftermarket or a factory race block?

I appreciate any help as I have a Giant shop full of his stuff
to identify and sort out! It is rather overwhelming for me
and I am not a novice on Mopar race stuff.

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Is there anything stamped on the vin pad? There is also mention in the Mopar Performance racing manual of a PN-3690030 block that was cast for Grand National use after the Hemi was dropped. The only problem to identifying this block is to find someone alive with a memory and a working knowledge of it. Also notice the reinforcing on the lifter bores. I acquired 1 of these blocks this summer and still have no definitive answer.

Randy