Welcome to the site...........just a quick note, i believe the LD4B intake has a different bolt angle the 64/65 273's. 66' and up would be ok. Not sure what year your engine is? If there is a mismatch, i know some have modified the later intake to fit. Just givin' a heads up to check it out.
My dad bought a 67 A100 for its engine and had that one rebuilt, so the engine in the van is not original. From the castings this is what I have determined:
Block: 1966 273
Date: 12-1-65 Night
Casting: 2465330-1
Bored .040" over (rebuild specs)
Crank .010" under (rebuild specs)
Heads: 68-74 273/318
Casting: 2843675-9
Intake: 66-69 273 2bbl
Casting: 2536559
The 67 had an auto and when my dad went to install the pilot bushing it was a little too big, so turned it down with a file and drill press. I assume the crank is a forged unit as the dampener looks like one for a forged crank and the engine runs smooth with it. I am currently looking for a set of 920 heads to rebuild to gain a little compression bump if any body has a set.