Need help with casting number!

[L30M20]

Hello everyone, I am looking at a supposedly L-78 69 Camaro, with a build date of 11b-X-66 code (late 69 car.) It has the single fuel line, 6kred/7k tach, "854" motor casting number,w/ J-20-9 cast date. Can not really see the pad to well, looks like T10 or 11, can not see the rest of it yet. The question is, I thought a "272" casting number block was used on all L-78's, am I wrong, since this a late car, did they switch to a different casting number? Thanks to all, Craig