At a point in time when Orange County was already using numeric prefixes but
Los Angeles County was still using alphabetic prefixes, I had occasion to
drive the western end of CA-22 into Long Beach; at the L.A. county line, the
Call Box numbers indeed switched from "22-" to "GG-".  I took particular
note of this because I had never been sure that the western stub of CA-22
(west of I-405) was actually named the Garden Grove Freeway as the main
section east of I-405 is; that call box prefix convinced me that it was.

My recollection of the boundary between the Hollywood Freeway vs. the Santa
Ana Freeway is that it was not at any of the interchanges.  Instead, it was
at a seemingly arbitrary location like Broadway (just east of CA-110).
Certainly the north-south portion south of I-10 (the northern one) has
always been part of the Santa Ana Freeway; it's the east-west portion
between CA-110 and I-10 (the northern one) that is at issue.

I use the phrase "I-10 (the northern one)" to refer to the discontinuous
portion of I-10 between I-5 and US-101.  Westbound it is signed as US-101
while eastbound it is signed as I-10.  As defined in:
http://www.leginfo.ca.gov/cgi-bin/displaycode?section=shc&group=00001-01000&file
=300-635
Route 10 is from:
(a) Route 1 in Santa Monica to Route 5 near Seventh Street in Los Angeles.
(b) Route 101 near Mission Road in Los Angeles to the Arizona state line at
the Colorado River via the vicinity of Monterey Park, Pomona, Colton, Indio,
and Chiriaco Summit and via Blythe.