You're right, the 9561(non ZL1) package carries an iron block 427 called L72.
I made a mistake in the production number i mentionned before, it is one of the ZL1 with the same options i want on mine!
I didn't find a complete list of the 9561 COPOS, GM built over 1000 of them so, i think any combinations is available..
But i do have found a picture of the exact replica of mine..LOL!!!
http://www.carpictures.com/vehicle/06L5G123110665/Chevrolet-Camaro-COPO-1969