A friend of mine has a documented LS-6 car, build sheet and all, but the engine bit the dust in '74, and they replaced it with a service engine.(don't know if it was a partial, a short block or what). I went up and checked it , and the code was strange.
TO417 C E H . The CE is faint, just barely visible, and the H is stamped out from the end, like a late addition. Then there was a # 13c202922 stamped at the edge of the pad, up close to the alternator. Any ideas about this? Just curious.

13c202922 is the CON VIN

1 - Chevrolet Division of GM
3 - Model year is 1973
C - Final assembly plant is in Southgate, CA
202922 - Last 6 digit of the VIN

So we know its a 1973 engine from a vehicle built at Southgate assembly and it would have to be a big Chevy car, as thats all they built.

TO417 C E H
T - Tonawanda Engine Plant
04 - April
17 - Day
CEH - Engine suffix code, cannot find this code so I can't tell you what it is. Maybe it something else?

One thing for sure, this engine was not a service engine. It came from a car as evidenced by the VIN on the block. Those were only stamped at the final assembly plant. So the story of a service engine is not correct, it appears to be just a used motor.

A service engine would only have one code on it and it would look like this; CE3xxxxx (x's a serial no) and no CON VIN.

I say go back and look closely at the suffix CEH and see if one of the letters could be something different.

If it is not one of these then I I don't know. The suffix CEH cannot be found in any Chevy info, interchange info or any of the other published data that I have access to. Would be nice to see a photo as I may have a different interpertation...
1973 Pass 454 suffix's::
CWD
CWJ
CWH <------This is the closest I find
CWL
CWK
CWW
CWU