To further complicate the 4P, pass around, code, it was used on early Z28 cars and later for L30/M20, 327 cars...
From CRG
The 4P code was not used at the start of production at either the Van Nuys plant or the Norwood plant.
Van Nuys started using the 4P code on the SS350 cars in September, but Norwood didn't start using the 4P code until October. Early Van Nuys SS350 cars and Norwood SS350 cars built before October will not have the 4P code to verify that they are SS's.
The 4P code can indicate either a SS350 or a L30/M20. Usage of the 4P code with the L30/M20 is believed to have started in the late December 1966 / January 1967 timeframe.

The very first 1967 Z28's and L78's were also coded 4P; the 4L and 4K codes were then used on the remainder of 1967 Z28 and L78 production.

The lack of a 4P, 4L, 4N, or 4K code indicates the car originally had a 327 (assuming the car had a V8, as indicated by the VIN). The only exception is the early SS350's noted above.

4P Hmmm 🤔
 

I didn’t know the 4P was used on that many different engine combinations. Hmmm 🤔.

I did not know the P code was used always thought it was 4k only. Appreciate the knowledge and information. TY!!

Realize that there are only about 6 4P / L78 cars known.

4P
 

That is insane had no idea!!! I really appreciate all the info and what to look for and if and when I find a real L78. Sean