I have a 1966 426 HEMI block 2468330-2 cast in 1 18 66 and a assembly date stamp on the bottom oil pan rail by the starter ear 3 27 66 and on the engine ID pad it is stamped BH426 WT with a Maltice cross and 4 2 23 What does the 4 2 23 mean? It does Not have a VIN stamped on the back of the block by the transmission mount.

Thanks Brian

That is the actual assembly date of the engine, April 2nd, 1966, the 23 is the build sequence

B = 1966 model year
H = Hemi Engine
426 = Cubic Inches
WT = Water Tested block
3-27-66 Pan rail is the original date the block was machined
Maltese Cross = .001" undersized bearing shells

*No VIN# was stamped into any block until the 1968 model year

I find it interesting that:
casting date 1/18/66 was a Tuesday
machining date 3/27/66 was a Sunday * what other numbers are stamped here?
assembly date 4/2/66 was a Saturday

Average '66 model year HEMI vehicle production was in the vicinity of 20 cars per day combined at 3 plants.

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Yes Dan, I agree, got it a wee bit wrong off the top of my head