Not "factory". You could buy all the parts to do it from Chrysler, but I don't recall there being a "kit" as such to do this. A 340 Six Barrel (in Plymouth parlance) was much more than just an intake manifold and carbs. The 340 Six Barrel engine had a different block, heads
, camshaft, 4-bolt main caps, manifold, carburetors, and air cleaner. Dodge used the "340 Six Pack" name (same engine though). I do not believe that Mr. Norm was swapping engines to build his cars... it was probably just an intake & carb swap.