There is a
lot of information available online about Gilmour's gear over the years; Gilmourish.com, and Kitrae.net, for example.
I'm not a Gilmour expert, but I did a little research a few years ago when doing some Floyd stuff for some guitar lessons I was taking. IMO, although Amplitube doesn't have the exact Gilmour gear, it has enough of the right sort of things to get you more or less in that zone. I've posted my own presets on the Facebook presets group, though others have posted theirs, too. You could go there and download a few that could serve as starting points.
IMO, the core of a "basic" Gilmour tone is going to be achieved with a Big Pig pedal model (i.e. "based on Big Muff") into the HiAmp (i.e. "based on HiWatT") amp/cab models, the amp to be set fairly clean.
For some Gilmouresque tones, that's practically all you need!
Obviously, though, delay is a thing for some Gilmour tones. Earlier on, he used the Binson Echorec which (sadly) is not (yet!) modeled in Amplitube. But you could use any of the variously modeled analog delays, like the EchoMan or T-Rex Replica or even the Fulltone SSTE. Gilmour has also used digital delays in his career, and Amplitube as a few options that would do the job, IMO.
Then, also famously, some Gilmour tones use one kind of modulation effect or another -- from either a Yamaha rotating speaker system or flanger or chorus pedals. Amplitube does model the Electric Flanger (i.e. "based on Electric Mistress", which Gilmour has used), though you could use other things like the Uni-V pedal model or the Leslie rotary speakers models or one or the other of the choruses.
If you spend some time researching Gilmour's gear and tones online (like at one of the sites mentioned above) you'll find all kinds of bits and pieces and details of information about gear and settings and how to emulate it. But I think the starting point is a Big Pig (a model which IMO could do with a refresh, but it does the job) that gets you your dirt, going into a clean but loud HiAmp. For a "Comfortably Numb" type tone, IMO that's
basically all you
really need, besides perhaps a
touch of analog-style delay. (There may be some modulation in that tone, but I don't really find it
vital. But you could put a
touch of that in there, too.)
Mr Gilmour's fingers are, alas, less easily replicated!
