Hear ye, hear ye @DannyP, et al:
I really like my Dellorto DLRA carbs. Most guys who have them really like them. There's not a single thing wrong with them.
But...
they're getting pretty old. New ones haven't been available for many, many years-- and lot of normal replacement parts come from "across the pond", from secret vendors (ALFA1750 on ebay, Eurocarb in the UK).
Weber IDFs are just so much easier to deal with. New ones are available everywhere. Figure on getting them gone through, even if they are brand new. This shouldn't be a deterrent, because you'll want to rebuild any used carb you find, so I'd figure on spending the money either way. Float heights, etc. will be wrong right out of the box, and there will be crud and snotty grease on everything new or used.
The good news is Weber parts cost less than anything else and are also easily available everywhere. 99% of the good jetting information on the internet is for IDFs. Most of the carb-whisperer dudes are really Weber guys at heart. The IDFs can be made to work every bit as well as Dellortos.
The only reason to get Dells is that the idle jets are really easily accessible and they made a 36 mm size that Weber didn't (if you have a small engine). Dellorto also made a Tri-Jet 48, but good luck finding anybody who has any idea how to set them up (after you pay $1500 for a set of "rebuildable" used ones). If I wanted to run anything bigger than 45 Dellortos (or 44 IDAs) at this point, I'd get 48 IDAs with the 3rd progression port-- everybody has good tuning advice for these as well.
Most carbs can be made to work-- but whatever you get, even if they are new, you're going to need to strip them down to the bodies, clean them completely, and reassemble them, setting float height, etc. With that in mind, I'd look at what you've got to start, and buy some IDF 40s if you don't want to stay on that road.