Help... 337 process/Musketeer Sport

Just a shot in the dark.....
I'm in the process of overhauling the O-320-E2C (150 hp) in my '68 Musketeer
Sport, model 19A, s/n MB-318. There is an STC available from Lycon to
install pistons in the O-32-E2C to increase output to 160 hp. This has been
done many times in the past on these airframes however the FAA has changed
the rules.

I need a 337 to install the upgraded engine on the airframe. I have two
examples of similar 337 however I now need copies of the "regional
engineering concurrence that the inspector had at his disposal in order for
him to approve the alteration".

Can anyone decipher that and point me in the direction of getting my grubby
little hands on this document?

Thanks.