I bought a s-42. A while back and was wondering does it take external or internal slave cylinder. Has the hole for the clutch fork. So I figured it is external. It's going on a 460.

 

Big block and diesel are external, small blocks are internal.

 

Does the slave bolt to the bell housing. And where can I get the linkage for the fork?

 

The slave slides into the u-shaped boss next to the fork opening on the tranny case. When you get the slave (or better, get a pre-built pre-bled master-line-slave assembly; waaay easier to install and no bleeding), you'll see how it clips in.

Not sure what you mean by "linkage". The slave rod moves the fork directly.