Hi,
If you mean the schematics for how to connect the radio in the car pls check this link to Hammars web site:
http://www.hammar.dyndns.org/~djhamma/wiring/wiring1968.htm you will find to diagrams for radio that may be of help.
If you look for the schematics for the radio itself I don't have them for a 68, but they are usually available on feebay in the Sams photofact "books".
For the 68 AM radio it is Sams book "AR-48" and for the AM/FM it is "AR-56".
I once collected all the AR# for 65-73, her they are for all to use (sorry i missed 64...):
FORD 5TPZ, 5TMZ AR-28 AM
FORD 6TPZ AR-36 AM
FORD T6SMZ AR-35 AM 8track
FORD F6TBZ AR-39 AM/FM
FORD 7TPZ AR-41 AM
FORD T7SMZ AR-45 AM 8track
FORD F7TBZ AR-46 AM/FM
FORD 8TPZ AR-48 AM
FORD F8TBZ AR-56 AM/FM
FORD C9ZA18805 AR-64
FORD C9ZA18806E AR-65
FORD C9ZA19A241 AR-64
FORD C9ZA19A242B AR-66
FORD D0ZA18806 AR-81
FORD D0ZA19A241 AR-79
FORD D0ZA19A242 AR-86
FORD D1ZA18806 AR-94
FORD D1ZA19A241 AR-94
FORD D1ZA19A242AD AR-104
FORD D2ZA18806 AR-129
FORD D2ZA19A241 AR-127
FORD D2ZA19A242AF AR-135
FORD D3ZA18806 AR-136
FORD D3ZA19A241 ?
FORD D3ZA19A242AB AR-153
br
Claes