I'm basing my comment on my 94GC layout which I assume should be much the same on the 3rd,gen. vans. The high pressure port on my 94 is by the compressor and is the larger of the two ports. The low pressure port is smaller in dia. and is by the firewall. I just dumped three cans of 134a into my system. I have a dual system and it tends to lose about three cans worth over the winter and about one can over the summer so that I have to add one can for the fall season. No big deal as Big Lots sells the stuff for $8/can.
I guess that Chrysler made a change to the layout for the 3rd. gen. vans. Just my $0.02.