Sizing the CB needs... Homebuilt wiring too

I am installing a used Narco AT-150A transponder and have only acquired
the pinout.. not an install manual.. (trust me.. if/when it goes, it
will be replaced rather than repaired..)

A brief/quick google search didn't bring up anything that indicated what
size CB to use..

What size CB is considered adequate for this type of transponder that
will allow enough current but still protect the wiring from a short?

Also.. those of you with dual navcoms.. do you have both nav-coms ganged
on a single breaker or separate?

It seems that most of the power draw would be during transmit only..

How many folks have wiring that by passes the master switch.. to a
clock, a cigarrete lighter/power power, a keep-alive circuit on backup
batteries in the panel...

Dave