318LA/906 SBE build it OR go Big block?

a big block swap is not very budget friendly.

most cost effective? getting running what you currently have and addressing all the other issues of operation and driveability-- brakes, sorting out that fuel line, probably wiring, tires and a battery will absolutely eat up a bunch of cash in a hurry.

then build a 5.9 on the side because you can use most of your LA 318 parts on it-- mounts, oil pan, etc.