S13 engine/trans mount, S12 transmission (71B or 71C, gearbox side bell bolt patterns are the same) with S13 SR bellhousing, that's all that's needed to get it mounted.
Wiring is kind of easy, depending on what year, and how exactly you want to do it.
BUT, you have another problem. The auto S12 chassis is different from the manual trans chassis. The trans crossmember mounting is different between the two.
Otherwise an SR swap is no harder than any S13 or S14. I did my SR20DE swap in a day, and had it running in two days... By myself. But I did months of research and planning before I did it.
Check out
http://www.club-s12.org for more info.
And always search, search, and search.