Ive seen other source, such as this that indicate that a C6ME-A block could be a CJ, such as here:
Cylinder Block | Mustang 428 Cobra Jet Registry
"Engineering numbers that appear frequently during the CJ era include C6ME, C6ME-A, C7ME, C7ME-A, and C8ME, but beware -- these markings do not indicate a specific block whatsoever,..."
and here:
Ford FE Engine Block Casting Numbers - FORDification.com
"428-4V, Police Interceptor, Cobra Jet"
Given that the guy who rebuild the engine said it was low mileage from an old crashed car, and it had the CJ heads on it, I'm thinking that the mystery digit is an 8 and it is a CJ build. Maybe I'm being too optimistic or I'm just looking for evidence to support the outcome I want.
damn you Ford and your cryptic ways!