318 build. what would you do?

Yep long story short is that yuou will spend as much or more on the 318. As soon as you decide to go much more than stock, I would get a used engine for $100-200 from a junker or someone selling one. Make sure your convertor and balancer are for the 360 external balance type and build the 360.

No replacment for displacement!
You will have an instant 50-60 HP and 60 or so more ftlbs torque all things being equal.