LZ4/LZ9 Cylinder head casting numbers

[Frank Reiner]

At this point I have seen two casting numbers for the VVT 3.5 & 3.9L cylinder heads. The last three digits are 610 and 746, respectively.
Are any significant differences known to exist between the two castings?

[SappySE107]

All of mine are 746 castings, so I don't have anything to compare with. Are the 610 castings newer?

[Frank Reiner]

The "610" casting number came from two sources: ebay ads, and this paragraph from Engine Builder Magazine making reference to the LZ4:

"Heads – The heads are all new and shared with the 3.9L. They have big intake ports, modified chambers with bigger valves and updated exhaust ports. And, the water outlets were moved from the intake surface to the front of the heads. We know of two castings, the 12590746 and 12624610 that come with or without holes drilled for A.I.R."

It may be seen that the "610" is a numerically later #; 126 vs.125.