Today, dollar for dollar, is the 318 faster than the 340 ???

So now we're counting carb and exhaust toward the budget??? Good luck with that budget now - on either engine.
Freshened 318 magnum, you will still have have around $1,500 for cam, intake, exhaust and carb if you want to run a carb or run fuel injection and get the ecu reprogrammed for your application for $250