[Roadsters] Brake Master Cylinder alternatives

[Eddie]

Hi all,

I've checked the 311s site, and there is some info on using a 510 master 
cylinder in the wiki section.  Someone else talked about using a 280Z 
master cylinder as well.

Since I'm not comfortable with the single reservoir system, can anyone 
tell me what master cylinders work?

Are those the only two?

What about clearance issues? 

Thanks.

Eddie