Refresh my memory. 4 to 2 + dual down pipe!

I just got my hands on a 4 to 2 manifold with dual down pipe. Came from an 86 Jetta 1.8L 8V Karat. Everything looks good. Now I need to know what I need to get to install this in my 92 Jetta 1.8L 8V. Both cars have digifart, the only thing I can tell I'm going to have problems with is the O2 sensor. right now in my 4to1 mani, it is threaded in there. The 4to2 doesn't have that which tells me that I'm going to have to put it in the Cat. Converter right? And if so, which VW converter do I get? Do I have to change the studs for the manifold? gaskets obviously, Can anyone help? Mind you this isn't going to be done until I get my hands on a cam,and so forth, so it won't be until early spring, So a little parts buy here a little there, then spring comes and my car goes ZOOM!