I don't know why people don't build more mild big blocks, could run 2.76 gears factory stall and still make a ton of power especially idle to 4000 rpms, ultimate driver.
you have a 318 2V car now think about what you need to get a BB in there:
mounts- 150~250
transmission- let's say you get lucky and score a $500 cast off
exhaust- what's the cheapest headers gonna run? maybe you scoop a used set for $500?
then: do you need a better radiator? does the power booster fit? power steering? gonna need to get that oil pan that fits and make sure your steering linkage is right. brakes up to the task?
so you're easily 1500 into it before a motor and other assorted sundries.