[xb-60]

Tim - I had a look around in the Registry pages. Here is some of the information I found, as well as my slant on it.
Cars listed in the same order as your photos.

CSX2345
Designated at AC Cars as “race car with wide rear wings” (cut-back door competition car)
My interpretation – left AC Cars with flares; may have had flares extended later

CSX2128
Originally a Shelby team car
Acquired “oversize spats behind front wheels and enlarged rear flares”
Current ‘spec’ is Sebring ‘63
My interpretation –probably left AC Cars with flares; flares extended later by SA

CSX2022
Active racer, received updates as they became available
My interpretation – flares probably added by SA

CSX2156
Supplied “unpainted, with body modification”
My interpretation – left AC Cars with flares; may have had flares extended later

No. #98 aka CSX2136
Delivered to Shelby American “unpainted, with body modifications”
Listed in AC Cars production records as Le Mans Replica
Further mods at Shelby American – pop- riveted spats and widened rear flares
My interpretation – left AC Cars with flares; flares extended later by SA

CSX2151 (Hairy Canary)
Gained widened flares post 2003
(owned 2002-2003 by Kevin Kivlochan of COB6008 fame)
My interpretation – flares added later

CSX2273
Probably supplied originally as a standard road car
My interpretation – flares added later

CSX2225
Probably supplied originally as a standard road car (luggage rack was as originally supplied)
“Extreme” flares added around ‘74
My interpretation – flares added later

CSX2192
By ’67 had acquired rounded flares, hood scoop, roll bar, Webers, 5 spoke American wheels
New body in ’79 after crash and substantial damage; rebuilt with large flares
My interpretation –probably standard body originally; flares added later

It would seem that most flares were added well after leaving SA's doors. Very few left AC Cars with anything different to the standard fenders.

Feel free to contradict or add info. There are plenty out there more knowledgeable than me.

Cheers,
Glen