do not install or charge a new compressor (FS-10) until you have flushed all the lines, and replaced the Condenser, Acummulator/Dryer. you can't "revive" Ford a/c systems, if it's dead, it's dead. Start from scratch and get a specialist to help you. Wait until Fall when a/c service prices go down.

If at all possible, try to adapt the compressor from the 4.0 liter Aerostar, the 3.0 compressor (FS-10) is garbage, don't bother buying a "new" one, it will fail in no time and then you're back to square one. OR, try to adapt a Japanese compressor like a Samden.

the compressor in the 3.0 liter Aerostar is bolted to the lower side of the block on the passenger side; The 4.0 liter compressor is mounted on the driver side on top. The only problem is adapting any other compressor to the 3.0 liter. You'll have to fabricate an adapter and get a different manifold hose, but regardless, don't waste your money on another FS-10 compressor, you'll be happy for 4 months and on the 5th month, kaput! I've been there, done that.