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

OK...
A 273 had 1.78" Int and 1.50" Ex valves
A 318 had 1.78" and 1.60".
A 340 (some) had 2.02" Int and 1.60"
A 360 had 1.88" and 1.60"
The 5.2 and 5.9 have 1.92" and 1.625 in closed chamber heads. The ports were raised just a little.
Per (my memory) the Magnum book by Larry Sheppard
Richard Holdener is doing a Dyno test on a stock junkyard 5.9 Mag.
Dead stock without running the pulleys and a short head pipe without mufflers got 288 HP @4300 RPM and 386 Torque @3300 RPM.