In anticipation of these manifolds becoming scarece I have been gathering these manifolds and now have a pretty good supply. Most I've aquired have come from Chevy/Furd swaps. The last manifold I saw at a Mopar swap was $250. The D4Bs with the Chrysler part number are now allowed in Stock Eliminator which makes them sought after. I have D4B's on all the 273s I have both in cars and on engine stands.
Just to clarify to other members, The D4B's are for 64 and 65 cylinder heads only. LD4B's are for 66 and newer 273/318 heads. They will bolt to 340/360 heads but because of their smaller ports there is a mismatch.