[Purple dye]

Stainless steels usually have a lower tensile strength than an equivalent size steel fastener. Unless the SS bolt was advertised by a very trusted supplier as better i wouldn't use it. Especially with the junk that is available thru most outlets. If you want to scare yourself sometime google "fastener quality act" and look at the good work our government ISN'T doing to protect you.
Use a quality never seize if the bolt doesn't have thread locker on it.

 

[Purple dye]

I'm not familiar with the assembly your talking about so i don't really know how the bolt is loaded. Allot of times the 12 point heads are used when there is a space limitation which goes hand in hand with a high load application and therefore it's typically a better bolt if it's a good supplier.
I looked quick and a typical grade 8 bolt is rated for 150,000 psi while most of the SS bolts are rated for 70-80,000 psi. I didn't have metric specs handy but you can see what i'm getting at with the strength tradeoff. If you choose to use the SS you should look up the torque spec. for it because i believe it will be lower.
Changing bolt type in a situation like that is sticky business best avoided.