Brandon,
Obviously by your post you don't seem to mind a non-factory set-up, but just to note, the 71-2 factory B body sunroof is the same as the 70-2 E body unit(electric), the B body sunroof went to a hand crank assy in 73, plus the deminsions change, basically the ASC supplied sunroof units were used by several other car manufacturers, the sliding steel roof panel has 1 or more sheetmetal ribs welded along the underside of the panel, and these ribs were rather crudely tweaked with plyers by the installer to affect a convex bow in the panel, so that it can be tailored to match the roofline of the vehicle it's being fitted to,....the cassette, or main internals of the sunroof are affixed by spot welds around the sunroof opening of the roof skin which is rolled into the cassettes opening, the rest of the casette, depending on what style/year you chose, is bolted, or welded to fabbed braces under the length of the main roof, ...so basically any solid panel sunroof that fits your desired opening deminsions, can be used, as you can alter the convex shape of the panel, as I described above,....obviously glass units are a different story, the Cadillac moonroof, as well as Lincolns are too flat to use on the 71-4 B body, a better alternative for a glass sliding unit is the early to mid 80's Chrysler Lebaron, I used componets from these units to repair/rebuild the 70-2 E/71-2 B body units, the glass panel shape is slightly curved along it's leading edge to follow the windshield profile of the Lebaron line, were as the E/B panel is straight, if that matters to you,...also the Lebaron is electric,....depending on your fab skills, you don't need the roof skin from the donor, just the cassette, the sliding panel, and related parts to make it functional, I use the vehicle that I'm installing the sunroof in, as the source for the opening, by laying/locating the sliding panel on the roof of the vehicle to be installed in, trace the outer shape of the sliding panel,then add an additional 1/8 " to the outside of this line, then shrink that drawn line along the inside perimeter of the line you've just drawn out approx 1 inch, that will be the opening deminson that you will cut open, the remaining 1 inch you can hammer and dolly down at a 90 degree angle, to create the lip needed to weld the cassette opening to the 1/8" you added to the intial drawn line will create the required panel gap, this way you eliminate a lot of welding/body work, if you tried to graft on a section of donor roof skin,...
The panel, solid or glass, when operating drops down, before sliding back, and just the reverse when closing, it takes quite some time to properly set one up,.....if you do get a unit, I do recommend you get the donors roof section opening so that you can study how the opening was formed, and reproduce it on the vehicle you decide to make a sunroof model of,....I did a number of 71 wingcars for a customer, of which he desired sunroofs in, so to quicken the repeated installs, I created a buck from to locate, and jig the roof for hammer and dolly work, your only attempting a single install, so basic hand work (hammer/dolly), careful measurements, and a cut once motto, you should be able to tackle the job, the other alternative is lots of cutting, and welding footage of seams, to graft in a donor roof, unless you happen on a B body full roof,
Goodluck, hope this helps
Mike
