there are 3 main styles of crankshafts for surface nitros,
the most used currently is what is called the SG crankshaft
this type of crank uses a standard through style clutch nut (no shaft)
the second style is called a short standard (threaded) style crankshaft.
typically the short threaded...
if you are using the stock flywheel, you will most likely be stuck with using the stock OE pilot shaft. you might be able to make one from another model work (for example the HPI one you posted, or even one of the cheap HSP ones), but with how the flywheel is set up it may or may not work. if...
https://img2.associatedelectrics.com/pdf/cars_and_trucks/shared/cutcrank.pdf
the write up from ae regarding cutting cranks down, slightly different but similar principal though.
the O.S. ones you listed fit the O.S. line for aircraft, i am unsure if it would work correctly on the XXXNT or even on the small block engines it takes.
you also might have to replace the flywheel/collet if you get a different pilot shaft, as it will have the hex on the end and will protrude...
that drive washer is not used on the XXXNT trucks, having that will push the flywheel further from the engine so the clutchbell will not line up properly.
as far as spinning over the collets, are you getting the pilot shaft really tight? when you replaced the collet did you also replace the...