Sorry, See where I misread now. FYI, it is my understanding that the LD4B is a 340 manifold and the D4B is for a 273. I am putting a 340 together and have a D4B, looking for a better fit for my 340, which is why I chimed in. Good luck!
No sweat, I know for 100% that the LD340 fits all year 340's, I have that for my 69 340, but looking for an intake for mine and dads 273.
For 273, there are a couple variations on that, as there was the D4B, LD4B. D4B is for an 65 and down 273, its no biggie, but the intake to head bolt hole is angled ever sooo slightly different. Mods can be done by hollowing out the hole slightly and voila you now have an intake for 66 and 67 273.
That D4B is worth $$ to some, maybe post it up in the trader section??
