318 Rebuild suggestions?

The high volume pump isn't necessary and most shops will run you off if you try to buy your own parts since they can make a good amount of markup on them.
If anything have the shop do the machine work and do the rest yourself.
If you can't do that look for a crate motor long block as a direct swap.

Just recently did a long block in a friends truck with a performance (315hp) for under 2,500 so all the time having yours down and the cost of machining and parts along with your own abilities needs to be weighed there.
Long blocks have a warrantee also.