Questions as to motor in my 1952 M38

Hi all. I'm new to the forum. I recently purchased a 1952 M38. I have a couple questions regarding the engine that is currently in the jeep. It appears to be from the 1950s, but I do not think it is the original motor for my M38. It is an inline 4 cylinder (I believe to be a L-134). The block on the driver side is stamped with the following number "646228-I-W4 AN1-CR-N2" and the top of the engine (just below the intake) is stamped with the following number "648830 1-15 C WF." I've tried to research these numbers and I've found some information on the driver side block number. I seem to keep coming up with a Willy's Truck motor, but I'm not 100% sure.

My jeep's serial # is: MC95888 (matching #s on the title and the ID plate on the dash to this effect).

Any help identifying this motor is greatly appreciated.

Thanks!

If the engine is a flathead engine, it is indeed an L-134. But, if it has a rocker arm cover, it is an F-134.

Engine numbers "should" be on a boss just behind the water pump, but if the head was planed or shaved, that number went away. Some rebuilders seem to have stamped the number elsewhere on the engine. On my F-134, this number I found after 35+ years of looking "may" be the original engine number.

But - I've had no luck in tying this number back to anything; CJ?, truck, bus, M151 or M38 or anything else.....