From what I've read in various BB threads here it appears that I need to pull the distributor in order to identify it. Is this correct?
The odds are good you have a Marelli (if the weights are above the points, it's a Marelli - if below, it's a Bosch). But yes, you will have to pull it to read the model number at the base.
Assuming that I do need to pull the distributor, can I just pull it without rotating the crankshaft so that cylinder 1 is TDC? That is, can I just carefully pull it, read its id, and replace it without perturbing ignition timing?
Yes, you need to remove the distributor to install the electronic thingy. Yes, you can pull the distributor without rotating the crankshaft. But no, you can't replace it without checking the timing. Substituting the electronic trigger for the points is going to change your timing somewhat. And even if it didn't, you can't re-install your distributor exactly
the way it came out. Plus, you will want to add a little more advance when going with electronic ignition.
Pertronix is my most likely option, even if I have to drill some holes in the mounting plate. However, how can I determine if my current distributor is a good host?
I believe a Pertronix is available to fit your Marelli distributor without drilling any holes. Several BB threads have discussed this, like the one at: http://www.alfabb.com/bb/forums/gt-1...de-73-gtv.html
. Or check out p. 6, which is the 8th page of the pdf file at: http://www.pertronix.com/catalogs/pd...tronix2012.pdf
Is the Marelli Plex preferable to the Pertronix? And if so, are the Marellis still available?
I don't feel that the Marelli Plex preferable to the Pertronix. Just finding one will be tough; they haven't made those things for 25 years or so. If you do find one, it's going to be used, so it may have broken wires, etc. Don't get me wrong - back in its day, the 'Plex was state-of-the-art - but now, it's a "period accessory".
Are there other electronic ignition options?
Sure, lots. But if you are on a budget, it's hard to beat the Pertronix.