Help ID this set of pedals if they are from Slant, 318 or HD style like 340 and BB darts

There are TWO pedal ratios; one for the slanty's 9.5" clutch and another for everything else.
If you are intending to use a HD B&B 3-finger clutch, then you need the V8 hi-ratio pedals. The higher ratio makes it easier on your left leg. And you need the HD version which has the matched O/C spring and it's support bracket. And because of the work this unit sees, it has bushings (sometimes called bearings) so that the pivots won't wear out prematurely.

If you are intending to use a diaphragm clutch,even a HD one, this is less important. However, I still recommend the V8 pedals, because they make the clutch easier to modulate.

BTW; the O/C spring also helps to keep the pedal down against the spring-pressure of the clutch. This is helpful if you spend time at stoplights and such. But the diaphragm clutches have less static pressure, so this spring sometimes ends up keeping the pedal on the floor. This is bad news at WOT, so you should consider a rev-limiter.