308 GT4 manual

This link will get you a pdf copy of the 308GT4 WSM (which is all that is available for carbed 308):

https://www.dropbox.com/s/rav0gzmzrcgpb4s/308GT4_workshop.pdf?dl=0

The wiring diagram is in your OM (if you don't have one, state what year and version 308GT4 that you have plus LHD or RHD -- this should be in your FChat Profile as well).

Another resource for you can be the SPC (Spare Parts Catalogue) figures available on the F part suppliers websites. Here's the one at Maranello Classic Parts for the steering rack from the 1979 308GT4 SPC for a LHD:

https://www.ferrariparts.co.uk/diagram/ferrari/308-gt4-dino-1979/030-steering-box-and-linkage

 

If you are talking about changing the bushings inside the steering rack look at this tutorial on this Pantera site, they use the same rack.
http://www.panteraplace.com/page203.htm