I found this list at GearSlutz, which seems pretty accurate, but I look forward to see carlaz's list.
American 12C = Jensen C12Q
American 12K = Jensen C12K
American Alnico = Jensen P12Q (or R)
American Bulldog = VHT G-100-E Pitbull
Brit Vintage 8 = Celestion Vintage 30 8 Ohm
Brit Vintage 16A / 16B = 2 different Vintage 30 16 Ohm
Brit Anniversary 1 / 2 = 2 Flavors of Celestion G12H Reissue
Brit Silver = Celestion V60
Brit V1 / V2 / V3 = Various flavors of Vintage 30
Brit 100 = Celestion G12K-100
Brit 80 = Celestion Classic Lead (More likely G12-80, thanks to Metrik’s sleuthing)
Brit 75 = Celestion G12T-75
Brit Alnico B = Celestion Blue
Brit Alnico G = Celestion Gold
Brit Alnico S = Celestion Silver Bell
Brit Darkness = Celestion / Mesa Black Shadow
Brit T12G = Another flavor of G12T
Brit Green = Celestion G12M Greenback
CV GT12-16 = Carvin GT12
California Red = JBL D120
EV Darkness = ElectroVoice Black Shadow
HiAmp = Fane Purple Back
Jazz 12 = Roland JC-120 Speaker
Metal V 1200 = Peavey Sheffield Model 1200
Silver Alnico = Whatever was in Silvertone Twin Twelve’s (Fisher maybe?)
1) Why does the same speaker configuration sound dramatically different across cabinets? I thought it would be more subtle.
That's the nature of cabs. Different wood, different coverings, different sizes, different placement of the speaker in back, open back vs closed back, etc...its all a factor. Its perfectly reasonable to me that different speaker cones would make a difference, along with the actual cabinet selection, mic selection, mic placement, etc.. You can also adjusted the cab size slider from 1-200%, which can somehow make the cab behave like its smaller or bigger...and that should effect the sound for sure too.
What is not clear to me, yet, is whether all this stuff in AT4 is accurate or not, or if they started with some base IR's perhaps and then are estimating DSP based on all of those factors.. Certainly it makes a difference when we slide these items around..and we can futz around until we get a sound we like, and ultimately that's probably all that really matters, but I have no idea if all of those factors are realistic and accurate..