L-head engine numbers

I looked at a 48 2A today. It ran really well, had the usual rust issues, floors, hat channels.....overpriced in my opinion, but I saw the receipts and the owner has spent plenty on it, but we all know that does not necessarily mean it's worth more...

I looked all over for the engine number and finally found it on the oval pad on the upper front passenger side of the engine, behind the oil filter. Trouble is the number was really odd. The first character was a little faint but it looked like a four...the whole number was 442-91509D. now from what I've read the engine number, if stamped on the side, should start with CJ-2a, and a J if stamped on the water pump boss. there was no number at all on the boss nor any indication that there ever was a number there. this made me think that it was a 46 or older engine, in the '48 CJ-2a chassis.

But there was another odd thing. From what I've seen so far the L heads are drilled and tapped for a heater water outlet in the left rear of the head. this head had the location cast but not drilled. Maybe this is correct for a 46 engine, but maybe also correct for an engine meant for a welder, generator or something besides a vehicle? The jeep had a period heater. They used taps on the radiator hoses to supply it with water.

Any ideas on that engine number? I'm continuing to search the other sites.....

 

Looks like it's a very early Willys Americar engine..

http://ww2jeeps.com/htm/amr44291362i.htm