M body caliper rebuild question

I have a 1984 M body brake setup for my sons car that i am collecting the parts up to rebuild. Heres the question. I am rebuilding the calipers. Or at least getting the parts together to do this. Calipers currently have soft dust boots are installed. Do i have to use soft dust boots when i rebuild them? Or can i use the alternate hard boots? Does it matter which? Is the caliper and piston machined specifically for one or the other?