http://web.ics.purdue.edu/~fishertr/alternator.html
Another conversion option using the alternator found on early '90s Saturns (Bosch unit?). I've done this one to my 1500, with great success. The shaft size is the same as most Delco alternators; I have several extras sitting around, so I pulled one off and installed it on the Saturn unit, after re-clocking the front housing. Side-by-side, the Saturn alternator is right between the Delco and Lucas, in terms of size. Hookup is a breeze, provided you have some basic knowledge of your wiring, and you can retain the use of your warning indicator. These, like the Delcos, are proven alternators. And yes, the Saturn unit is self-exciting.
My MkIV came with an internally-regulated alternator, so the modification was minimal. I've done a similar conversion to my '66 Oldsmobile, which used a 43-amp external regulator Delco (now a self-exciting 100-amp internal) originally, so it should be possible to eliminate your regulator wiring altogether as I did. Be forewarned - it'll require cutting the loom tape/wrap from your harness... Something you may not want to do with a cloth-covered harness.
It's cold, damp, dark, and drafty with the top up and headlights on... British motoring at its best!