If the customer is wanting a stock stroke 340....... then that’s what he’ll get.
If the conversation drifted towards the area of, “is there anything we can do to get more power out of it, and still keep it very streetable”....... at that point I would have mentioned a 4” crank would be my preferred choice for that kind of result.
As far as the “huge” added expense of the 4” crank...... according to what you’re saying...... it looks like it’s a bit more than twice the price of grinding the stock one.
Your experience with stokers and mine differ.
I don’t find the added cubes to have much of an effect on the peak rpm.
Sure, they lower the peak a little, but certainly not to the degree you’re inferring.
Last year I had a 360 on the dyno that was very similar to the 340 you’re going through.
9.7cr, pump gas, bowl blended J heads(230cfm), Old school dual plane, afb carb, .500 lift ex manifold friendly cam(.842 design).
Dynoed with headers, peak hp occurred at 6200, and it was only down 5hp @6600.
Your position is that by putting a 4” crank in that motor, it would drop the peak by 1300rpm(peak at <5000).
My position is it wouldn’t.