273 4-bbl Hi-PO Engine Appraisel?

Ok, here is the skinny on the engine I have:

Left front deck area in front of head: Cant find anything, sorry!
Casting date on side of block: 1-8-69 and a "ND"
Casting number on block: 2806030-2-73-4
Intake maniifold #'s 2536563 date: 12-5
exhaust manifold#'s 2465769 date:1-10-69
other exhaust manifold# 2780945 date: cant make out, sorry!
Carter Carb # 4305 S

Now, on the right side of the block near the pan, there is a machined pad. There is nothing stamped into this machined pad. Its clean, clear and "empty!"

Can anyone tell me what all the above numbers come back as??

Aaron