Oh well. Couldn't wait for replies. Seemed like a good deal, so I bought a Porter Cable Mark II milling head today on eBay. Looking forward to getting it. It has the 2.25" shaft, though, so I'll need to turn it down to 2" to fit the overarm bores. However, the head itself is in good shape and appears to have had an easy life with little use in its time. The seller says it has a MT-2 spindle, so tooling for it shouldn't be too hard to find. Comes with a 1/2" collet. Most of these heads, from what I read, though, came with a B&S-7 spindle, so we'll see if he's right.
I've been spending quite a bit of money getting this thing tooled up. Once I get all the stuff I've bought in the next couple of weeks, I'll have a good start on things. I have bought a hold-down kit from Shars, a couple of end mills, a set of 1-2-3 blocks, a right-angle block that I think is going to be too big, the milling head, and some odds and ends.
I'm still going to need a vice at some point, a 4" I think, and a larger fly cutter than what I have, as well as a decent face mill, a couple sizes of T-slot cutters, and a couple sizes of dovetail cutters. That should get me through the projects I have in mind at this point.