Intake info needed !

for reasons that I have so far failed to figure out the location of the two planes of the runners are reversed between LD4B and LD340. The LD4B started production in 1966 (for 273) when the intake bolt angle changed (early 273 took the actual original - D4B) and the LD340 came out in 1968 with bigger ports. But all the runners that were high in an LD4B are low in the LD340, and visa versa.

Would welcome an explanation if someone has one...

My first aftermarket manifold was an LD4B bought new in 1976 - it cost about $100 at Aberdeen Speed Shop on Rt40 in Aberdeen MD and the new 600 Holley cost about the same. It was a huge investment for my 318 1970 Dart