Sorry for the delay in responding, but here's some data on alternators from a handy little booklet called "Lucas Fault Diagnosis Service Manual" - a freebie given out to registrants at the '94 All-British Field Meet in Portland, Oregon, USA.

The 4TR voltage regulator appears to be fairly standard and the local parts store threw one in when he sold me a brand new-in-the-box 11AC that was, as was stated, an original option on late IIAs.

The AC alternators require external regulator. The ACRs are integrated. Maximum outputs are listed as such:

 
10AC    35A
11AC    45A
11AC*   60A (*25380, 23633 - numbers similar to those on the yoke of mine)
15ACR   28A
16ACR   34A
17ACR   36A
17ACR*  25A (*derated)
18ACR   43A
20ACR   66A

This handy little tome has testing procedures, other values, etc. Don't know if it's still available. The date on this one was 2/94. It says "Catalog No. 9001" and comes/came from Lucas Aftermarket Operations, Lucas Industries Inc. Troy Michigan (Printed in USA).

BTW, I still haven't had time to replace my C40 genny with the 11AC, so all data is as Joe stated it (not necessarily reality!).