Nick, depending on if these are flat all the way down you will need to use the spacers...they are adjustable width, and have 2 spacers that can be put on each end or togther to adjust width.
if they are solid, then the width is not adjustable..
but if John doesnt have them, you will need to either use the stock ones that came on the IQ skis...or call holz and get them from them...
just use grade 8 bolts to mount these...no special hardware needed.
as for Holz not selling them, not sure....but i do know that polaris developed an IDENTICAL spindles on the 2010 IQRs that look like Holz...and are much cheaper now too...about $215 for the set