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

Well
here's what you do;
buy the early hi compression 340; sell the heads, sell the used cam.
Install any half-decent junkyard heads and a free 318 cam .
Now you have a big bore 318 with a serious bottom-end that will burn rubber with 3.23s to say 80 mph or more.
I have done this and highly recommend it.
I got the 340 for free because it had sat in the junkyard with the intake off, and some of the pistons were seriously pitted; no big deal. I got the 318 heads for swapping the 340 junk onto a buddys 69 Satellite 318. So I was into this thing for gaskets, rings, and a few hours work.
And, I had to buy some headers to stuff it into my 65 Valiant wagon.
And I had to buy a V8 904/ with attached 273 to get the power out the back door. Plus I wanted the adjustable rocker gear. So that was another $50.
The thing went like a raped ape; even with the 2bbl top end on it that also came from the Satellite.
That was about 1974, and was the most fun I ever had, until 1999 when I built my current ride.