Not to be a smart *** but the 273 Commando was not available in 1968. The 273 was still available. 340 was added as another engine option in 1968. Also, what is a bare long block?
Yeah the 273 was still available after 1967 but was phased out by the 318, the 273 Commando was no longer available after 1967 The Famed 340 phased it out.
A bare long block is a engine without an intake manifold, exhaust manifolds, oil pan, water pump, etc. It would be block with heads ready to assemble the exterior components. No accessories. A complete long block is everything from fan to flex plate.