mari115 i am not sure about the 3186.
But the 3185 does fit into the 5 digit case from JF. I recently made one for myself. I dont think there is anyone out there that could add ss into the case. I had read multiple post in rwi about a franken 16710. So far no case that is suited for that. Only way is to get a gen case.
the reason why i am concerned about this movement is the gen also have issues with the spring. You can read more here.
http://blog.watchdoctor.biz/2018/02/24/rolex-3185-vs-3186/
the 3185 hands will wiggle. But 3186 wont but there is a design risk that spring might break. And knowing very well is very difficult to source the rep parts can be my concern to even start with this movement.
we have to wait till one of the member open up for us to understand the design.
hope this will answer your question