86' GT oil pan question

My suggestion: Get a 7 quart oil pan and keep 5 quarts in it (windage). You don't need the oil level sensor (just a continual leak source if you ask me).

That option aside, you can just reseal the pan and dipstick that you've got unless it's destroyed or something.

86-93 5.0 Mustang oil pan gasket and oil pump removal & replacement

Been there, done that - You can do it in the car, but it is hard to do. The best way is to pull the engine.

Disconnect the battery at the battery ground terminal, remove the fan and fan shroud. Both motor mounts will need to have the large nuts that secure them to the frame removed. The trans mount will also have to be loosened, and it is a good idea to remove the drive shaft.

The rear driveshaft bolts are 12 MM, 12 point, and require a first class box end wrench (ring spanner if you are English or Canadian) to remove them. Don't get cheap here or you will regret it. I set the emergency brake and apply a foot to the wrench to loosen the bolts. Notice the paint marks on the driveshaft & rear end flange: align them the same way they came off. If there aren't any marks, get out your paint spray can & make your own marks. Have a catch pan in place to get the fluid that comes out of the trans when you pull the driveshaft yoke out.

I also had to disconnect the cat pipes at the headers to get the engine high enough to remove the oil pan. Be prepared to have to drop the steering rack and disconnect the steering shaft. The flex coupling for the steering shaft needs to be disconnected before you can get the rack out. You should disassemble the coupling by removing the 2 bolts that hold it together. Jack up the engine with a wood block under the oil pan and watch for things that bind or hoses/electrical wiring that may need to be disconnected. I put a couple of wood blocks between the headers and the frame to support the engine. You will likely need to jack up the rear of the transmission as well to get the required clearance.

Scrape the pan mating surfaces clean as possible - old gasket stuck to the surfaces are a source of leaks.

Get a high volume/heavy duty pump, and a replacement HD pump shaft. FMS makes one, and ARP does too. When you install the pump, the funny looking washer thingy goes on the part of the shaft that fits into the hex socket in the distributor shaft. It keeps the shaft in place when you remove the distributor, which you will have to do to prime the pump. Forget to put it on, and the pump shaft can come loose and fall down in the bottom of the oil pan.

There is a one piece oil pan gasket which will help re-assembly if you can find it. If you can't get this gasket, use weather strip adhesive to secure the cork gasket to the pan rails and the rubber strips to the bearing caps. Use lots of Acetone or MEK to clean the gasket surfaces so the weather strip adhesive will stick good. Read the instructions on the adhesive carefully to make sure the gaskets are permanently stuck in place and won't move when you slide the pan in place. Use lots of blue silicone sealer on top of the front and rear rubber seals where they mate with the pan.

Fill with oil, replace the filter. Reconnect the battery, switch the ignition on to enable the gages,
but DON'T crank the car. Remove the distributor and use a 1/4" hex socket to turn the pump counter clockwise (same direction as distributor rotation) until you see oil pressure (an external gage is a great help long about now). And keep turning for about 30 sec after you see the pressure come up. A reversible drill is the best tool to use to turn the 1/4" socket. The pressure should come up to about 50-80psi with cold oil. Once you see good pressure, check for obvious leaks, and then and only then, lower everything back into place and bolt down the mounts and anything else you had to take loose.

Putting the distributor back in is fairly simple. Pull #1 sparkplug, put your finger in the sparkplug hole,
crank the engine until you feel compression. Then line up the TDC mark on the balancer with the pointer on the engine block. The distributor starts out with the #1 plug wire lined up at about 12:00 with you facing it. Align the rotor to about 11:00, since it will turn clockwise as it slides into place.
Align the distributor rotor up with the #1 position marked on the cap, slide the distributor down into the block, (you may have to wiggle the rotor slightly to get the gear to engage) and then note where the rotor is pointing. If it still lines up with #1 position on the cap, install the clamp and bolt. If not, pull it out and turn 1 tooth forwards or backwards and try again. Put the #1 spark plug back in and tighten it down, put the clamp on the distributor, but don't tighten it too much, as you will have to move the distributor to set the timing. Note that if it doesn't align perfectly with #1 position, you can turn the distributor until it does. The only problem is that if you are too far one way or the other, you can't turn the distributor enough to get the 10-14 degree optimum timing range.

Set the timing with the engine running using timing light (don't forget to disconnect
the SPOUT plug and reconnect it when finished) 12-14 degrees BDC is good. Start up and check for leaks, let it warm up and look again for leaks. It took me 2 days plus, but I am old and slow, maybe your granny is faster.