Some P-30 chassis had installed an AC condenser w/integral oil cooler (1 unit). The oil cooler resides in the bottom portion of the unit. I'm in the process of replacing mine in my 1994 GM P-30 Southwind Storm 28ft.
The part in question is here:
http://acmeairparts.com/rvacheaterpa...egory=16022430
In the 2nd pic you can see the oil cooler connections. On the left side is the drier bottle connection and top right the discharge line connection. The unit sits via J channel on the bottom side then is tilted forward against frame and bolt via (3) bolts.
The problem is they mounted it metal-metal and vibration can crack the tubing. Before installing use some 'cut to sized' pieces of 'bicycle inner tube' and the pieces where the condenser fits against any metal. This will greatly reduce shock.
The following is a schematic of the condenser/oil cooler...
https://www.dropbox.com/s/3jtwk6g774...ooler.jpg?dl=0
The GM hose fittings for it are either sized 1/2in or 5/8 YN fittings
AC drier bottle is 3/4-16UFN