For grins I went to their website and as always Chevy stuff comes up first. I entered pistons for a 360 mopar and it said fill out the form below and they would contact me. I didn't see any listing for the sbm's at all
OP sounds like he knows exactly what he's looking for. I bet a message or phone call would be the best way to find out what they've actually got in stock to ensure a smooth experience.
My local machine shop got stuff through them when they worked on my engine a couple years back. No problems.