[OG68]

There appears to be no visual difference between the two manifolds apart from the casting number and the positioning of the 1-2 cylinder numbers.
The changeover date from the -140 manifold and the -234 appears to be around March 15-16 1968. This is also the time frame of the first casting of the RA II engine.
Coincidence?

The -234 manifold was carried over to the '69 model year.