Does this motor number identify the motor as being an actual 327 In my 69 commander?
Yes, at least originally. The casting number on the back of the block(front on a Q because they're backwards) , left side just behind the cyl head infront of the flywheel is the only surefire way to confirm it's still a 327 as many get swapped for 350's.
Ditto to what Mike Said. The ID Tag on the exhaust manifolds will show what was originally installed. However because 283,307,327,and 350 all use the same base block, it is very easy to swap and upgrade while leaving the tags in place for "look". As Mike Stated, get the casting number off the block (Google GM Casting number locations) and they will show you exactly where it is.
PS, Sometimes exhaust mans are bought used on ebay etc and the tags would be inaccurate. (Why anyone does this for SBC mans is beyond me because they are still available new.