Kirley,
I can really only help with numbers for the K15 coaches.
I have divided them into 2 lists: those which went to CIE and those to the UTA on the break up of the GNR.
To CIE:
264
63
65
75
78
93
97
140
168
195
To the UTA (UTA number in brackets):
262 (402)
263 (404)
32 (400)
77 (406)
81 (408)
Neither list is complete but as you can see, GNR coach numbering was not exactly logical.
I don't know which were wired for operation with the AEC railcars.
In regard to transfers, a few suggestions.
Studio Scale Models do a full kit for the K15 which I believe includes transfers. An email to Des O'Sullivan might help.
Also, Railtec Transfers do some Irish stuff.
Finally, there is Sunrise Transfers in Glasgow who do transfers for buses, including the GNR. These might work.
I am watching your build very closely as I am pondering buying the Worsley Works bits for the AEC's.
Best of luck.
Glover