Slant 6 block casting numbers

I think the 3338 is the date (on the 10,000 day calendar) - that would correspond to:
Day 3338 is Thursday, September 17, 1970

For the casting number, I think you're looking for a longer number - 7 digits

http://www.earlycuda.org/tech/engines.htm

(Also has a table with what the casting numbers correspond to after the text I've pasted below)

To find the engine number for slant six engines, check the passenger side of the block just below the head. For V8 engines, check the drivers side front of the block below the head.

The engine number contains the build year and engine displacement. It may contain an assembly date. The assembly date may be as simple as 3-15 (March 15th), or based on the 10,000 day calendar (2787 = March 15 1969).

The simple date is decoded like the so number on fender tags.

The letter before the number is the model year A=1965,B=1966,C=1967,D=1968,E=1969,F=1970,G=1971,H=1972,J=1973,4=1974.
Example… B-273-A24 reads as...1966-273cid- October 24th