I have a ‘70 M-code 351 C. Where can I find the
Serial number on the engine? Thx.!

On the back of the block just below the head on the Drivers side. Here is a picture of my 351C.

Thank You.
M-Code engine is in the car.
Any other more accessible place to verify
Numbers matching?

Dennis, it IS possible to view the engine VIN stamp with the engine installed. Try using a mirror tool, or even sticking your phone back behind the driver’s head and snapping some random pics, or taking a short video. It’s not easy, but can be done.

This one I spotted with a mirror and then used my phone to get a good shot of it ~ plus I had to do some cleaning of the area. I had many garbage shots before I got this keeper.

Thank You.
I will try this!

Mine is also a 70 M code, and had a weak stamp. I had to move the transmission vacuum line and the kickdown rod to get my phone down there. Still didn’t see it until I wire brushed the area with lacquer thinner. Thanks to everyone here for helping me find it!

Automotive Archeology!

I love finding stuff like that…

While you are crawling around your '70 M-code / Cleveland engine, take a look at the front passenger side of the block on the machined area next to the timing cover. There you should find the engine assembly date stamp. This can be an easier option than pulling the starter to view the block casting date and can be useful when trying to determine what parts are original to your engine (original parts will typically have date codes approximately 4 weeks earlier than the assembly date of the engine).
351C_Assembly_Date (front pass side).jpg

Yes, and there is also a machine date stamp under the oil pan gasket.
On my car, the dates all fit together like this:
Intake manifold casting 9J20 = Sep 20. 1969
Oil pan bottom stamp 9 24 69 = Sep 24, 1969
Head casting 9K2/9K8 = Oct 2/Oct 8, 1969
Block casting 9K7 = Oct 7, 1969
Oil pan block stamp 10 9 9 = Oct 9, 1969 machining date (which agrees with the K 9 date on the engine tag)
Front timing cover block stamp 9L21 M = Nov 21, 1969 engine assembly date, M code
Transmission tag L25C = Nov 25, 1969 assembly date
Like Mike says, most other original engine components are dated in Oct and Nov 1969
Car was assembled on Dec 8, 1869 - the Monday after the Stones ill-fated concert at Altamont.

Do Windsors have similar stamping locations?

What about the H code Clevelands?

Yes, they will have a VIN stamp in the same location.

The H-code Clevelands should have the assembly date in the same area, but the Windsors may not.