Technical flathead cadillac engine id

So I picked up this Cadillac engine from a fellow HAMBer john walker, thank you very much.
It came out of a 1940 and I have no reason to believe it is not a 1940 engine but..
My book says that for 1940 the seven digit identifying number is stamped on the crank case behind the left cylinder block, what I see is a six digit number with the second digit being a letter E.
Anybody familiar enough with these to help decypher this?
It's clearly stamped 6E2718

 

Paul mine is out of a 1941 Limo with a number 834HC13, thats on the right side of the block
just in front of the head, it has another number at the back of the block.

 

1. 6 is the (60 series) Fleetwood, eg. 3 I believe is the 75 series;
   
2. E is for 1940. A being the first year of use of the monoblock in 1936, B is 1937, C is 1938, D is 1939, E is 1940, F is 1941 and G is 1942; and
   
3. Sequential numbers.

Tank engine #s were different again. M5 & 8 prefixes were 1G, M19 & 24 were 3G

Note the engine number on this car 6E2512, yours is 6E2718. Total production for 1940 was 37,176 of which 24,130 were La Salle and 13,046 were Cadillac.

 

So what is an HC motor mgtstumpy?

 

I kept on googling but had no luck trying to work that one out. I'll try a little later and test my patience. What about the Cadillac La Salle Club, they might have some more specific technical information?

 

Engine sizes came in 322ci in La Salles and 346ci in Cadillacs.

A bit more inconsistency!

http://www.flatcaddy.com/downloads/1940 -1954 Motors/40-54 Motors-4.jpg
http://www.flatcaddy.com/downloads/1935 -1942 Motors Specs/35-42 Motors Specs-3.jpg

http://www.m24chaffee.com/cadillac-flathead-v8-engine-data.html

Tank engine #s were:-

• 1G Engines - M5 & M5A1 Stuart Tank, G103 Series
• 2G Engines - ?
• 3G Engines - M24 Chaffee Tank G200, M37, M19, M41
• 4G Engines - LVT 3
• 5G Engines - British CPT 20 (Very late war, T-16 looking, enlarged, longer & wider)

 

I believe the other number at the back of the block will be your actual decodable number. My '38 has a totally different number that made me thing it was a non-original engine to my car. However, after more careful looking, I found the correct number.