Hey John,
From a bang for the buck and not knowing what you have or need for that matter it is very hard to give you good direction. By tired what do you mean????? New valve springs are an insurance purchase to keep them from hurting other parts if 40 yrs old now.
Are you able or willing to turn wrenches yourself? If answer is yes, pull her out and pull her apart and repair/replace as needed. If answer is no then buy a crate engine but keep your old engine until you understand what it is and what all is worth. To gear heads an early 70's hot rod engine may be full of coveted casting #'s and parts.
Buying a crate engine with 400 HP is easy to do for about 3 to 4 grand and will have a warranty of 3=36 as a side benefit. I would guess if the old engine is running now some rings, bearings and valve springs and a gasket set with
oil pump while you are there will do just fine and that can be done for less than 500 bucks as a do it yourself deal VERY easy!!!