what are the advantages to a taper pin as opposed to a normal pin, or a
grade 8 bolt? would the pin be behind the collar or through it?

The collar will be the platform for a roll bender die setup and it will
be subjected to a thrust load, so I was considering cutting into the
shaft to make a notch for a heavy duty clamp collar to sit in. so say,
buy a collar for 1.375" or 1.25" shaft and turn that notch into the
1.5" shaft. that baby would never move, right? The shaft could be
ordered with a keyway full length, and I could settle for tapped holes
in the ends rather than stepped down thread. Also, easy to
replace/service if it all crapped out on me..

Thanks guys
- LP