Does the '94 Aerostar starter have shims for proper installation?

no the 94 model does not need shims for proper starter installation.

Additional information re starter replacement:

I replaced the starter on my 95 Aerostar, and there are somethings you should be aware of. The starter is located on the left (driver's) side of the engine. It is easily accessible just behind the front wheel. I used a floor jack and jack stand to lift the van for easier access.

If you don't know what you are doing seek professional advice. NEVER get under the vehicle when it is just resting on the jack, unless your nickname is "pancake"!

Disconnect the battery. Once under the vehicle disconnect the two wires on top of the old starter motor. One is the red cable from the battery. It has a ring terminal and can be removed with a 13 mm socket. The other is a wire from the ignition. On my original unit it connected to the starter with a spade connector. It just pulls off. The replacement starter (remanufactured and bought at Advanced Auto for $95) has an upgrade to this wire/connector.

Three bolts hold the starter to the transmission housing. They require a 13mm, deep socket for removal. I suggest using penetrating oil or WD-40 to help loosen the bolts. I also recommend using a 1/2 in drive ratchet to get the necessary torque to loosen the bolts.

Remove the three bolts. The two on the top and bottom are typical hex-head bolts (13mm). Remove these first. The middle bolt is different and looks like a threaded stud with a bracket on it. Put the 13mm deep socket over the threaded end and you will find the nut in the middle. This bolt only needs to be loosened until the starter comes off. Leave it in the transmission housing to ease locating and attaching the new starter.

The original spade connector on the ignition wire allowed water to penetrate the wire and cause corrosion. The replacement requires you to cut off several inches of the wire, strip 3/8 in, insert it into a splicing connector and then crimp it. (Not real easy lying on your back under the vehicle). This has to be done after you install the new starter. I also suggest you remove the nut and lock washer from the terminal on the starter that the red battery wire connects to BEFORE installing the starter. It is harder to remove it when the starter is on the vehicle. Don't loose the nut and waher.

Cut, strip and insert the wire into the connector on the end of the wire coming from the new starter. Crimp the wire, and then use heat (I used one of the long neck lighters and ran the flame directly over the shrink wrapping) to seal the connection.

Connect the battery wire to the starter, reconnect the battery and the test BEFORE you take the vehicle off the jack stand.

This is an easy repair. It cost me about $100 (had to buy a 13 mm 1/2 in drive deep socket at Lowes for $8). The alternative was to have the car towed to a shop and spend probably $300 or more to have this done for me, and wait several days. I HATE repairing cars, but this was easy enough and saved me money and time.