Your not going to gain any performance from the bore, the only performance increase you'll se will be from the pistons. The amount depends on the compression ratio you go with.
Rods and pistons will run you about $900 (wiseco and eagle).
Head work I'm not sure on price, but depending on what you have done, anywhere from a few hundred to a few grand depending on how far you go.
If you just do cams, springs and retainers, you'll see some bump, but if you do valves and P&P, port matching, etc you'll see more gains....remember to get the most out of the set-up you'll need to tune it.