I have a 1965 Dodge Coronet 500 that was equipped with a 426W engine. The production date for the car was December 14, 1964. The original engine is no longer with the car. If I was to look for a suitable date correct engine what would I look for? Something made in the October or November 1964 time frame?

The ASSEMBLY date of the engine is more important than the casting date. Most were assembled very shortly before the car was built, a few days to weeks is the norm (although sometimes it was many months). The thing to keep in mind is that your cars Scheduled Production Date is only the planned production date, it often varied by days, weeks, or even months before or after the SPD.

Also to consider is that the upper pad stamping should be stamped:

A426 HP
(assembly date, example: 12 02 for December 2nd)

The "A" = 1965

I didn't know the street wedge was an HP engine. Do you have a picture of an original 426W ID pad? I'm not sure I've ever seen one. I've seen A426 blocks before but not anything that said A426 HP.

I'm more familiar with the ID pad where the HP is on the second row with the date. So I was thinking it would be A426 on the top row and then something like 11 23 HP on the bottom row. But I don't think I've seen an original 426W block.

HP could be anywhere but yes, usually down below somewhere, here's one that's had a rough life but you can still read it.

Here's another example, obviously the HP stamp is different and in a different location. This larger font is more typical of a Marine Division font usage (special engines such as Max Wedges, 300 Letter Series, etc. engines were built there) but I have no doubt that this one is genuine.

Yeah that bottom one would probably be perfect in my car with a production date of mid December. I've only seen those large font stamps on MW engines and those are few and far between.

I remember about 30 years ago I saw an ad for Mopar engines for sale in the newspaper. The guy had a bunch of MW engines sitting in an old shed. I had never seen the large font stampings before but all of his engines had big font stamps. I think he had 4 or 5 MW engines sitting in that shed.

Agreed that date would work for yours just fine, funny, 10 16 is my dads birthday

Only problem is that 10/16/64 was a Friday so that engine was probably missing the rings or maybe the head gaskets or something like that!