45 year old springs = .02 $ a pound at the local metals dealer.
They would be marginal with the stock cam and 2 bbl.
You don't need a ton of pressure , but you do want consistent pressure.
130ish on the seat and around 300 open is pretty close to where you will want to be , and if you put in better rockers now , you'll thank yourself later.
H.D. stamped at a minimum , and any adjustable would be my first choice.
You don't need T&D's , but Hughes rollers or Crane ductile are not terribly expensive and you will not punch the pushrod through the rocker with either of them.
Here is an idea of pricing at the bottom of the scale , and even the H.D. stamped rockers would be a wise investment. http://www.summitracing.com/search/?keyword=MoPar rocker arms&dds=1