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

Yes the best bang for the dollar with new parts is probably crosswind intake speedmaster heads on a zero decked short block with something like comp cam xe268h-xe285h (similar from other companies) depending on what level you want to go also with gearing and stall. That would be with 318/340/360 take 360 out of the running and have to pay $1000-$1500 or more for a 340 would just leave 318. And be a strong one if they put enough gear and stall behind it. Most leave out gear ratio when talking small displacement 3.55 might be a nice compromise gear for a 360 but it's a highway gear to a 318, minimum 3.91 should be behind any well built 318.

But for cheap cheap dollars people should be doing running Magnums either 5.9l or 5.2l either should be good for 400 hp with cam 4bbl headers, the Chev guys are getting slightly more with LS 4.8l 5.3l and are making those swaps like crazy here few are taking advantage of this cheap power.