Well the block is in fact a 273. According to number on front of block. I bought a 340 manifold for $150. Probably going Holly since I have one on the shelf. I think it's a 380.
Found a place in Fairmont, GA called AMS Obsolete. This guy has 600 Mopars in his junk yard. Lots of Darts and Valiants. A few Cudas and a lot of "B" body stuff. He has a warehouse with over a million NOS parts. Incredible place! I bought both bumpers, rechromed, $325 ea., manifold, $150 and one piece of trim that I was missing, $68. He has several other things that I'm going to buy if he still has them when money is available. If you are needing something, call him (Mike). 706-337-4606.
Tom