a/c help needed.

[HTX86chevy]

the a/c works really good on the freeway, im assuming because there is major air flow to the condenser. it even works (not great, but ok) in stop and go traffic... It does not work however when I am parked. blows room temp. air.

I know some guys have went the E-Fan route but my truck is not overheating, in fact the engine temp stays @ about 180 constantly. so I dont want to bother with E-fans..... The a/c had to have worked great when these trucks where new back in the 70's & 80's so my question is:

how can i get the a/c system working like it was intended to even at slow speeds or while in park? any ideas? Im still running the r12 system and don't want to convert.

1986 swb 5.7, 700r, 4barrel q-jet, engine is bone stock .