91 mustang lx

So you're just swapping out the shortblock? The only issue I see with this is the 87-90 block doesn't have the provision down at the crank pulley for the crankshaft position sensor due to the DIS ignition system used on the dual plug engines. The 87-90 block can be made to work with your 91 wiring but you'll have to drill 2 small holes to mount that sensor.

Drill and tap. I would take the timing cover off of your 91 and down at the crank pulley you'll see that sensor. It has two pretty small bolts that hold it on. The wires feeding it go behind the back of the timing cover and up to the harness.

XxFaceYourFear said:

Cool, I will definitely be doing that. I may have a 2.3 from a 96 ranger available as well, so whichever is in better condition will be used for the swap. Also, I'm planning to do a 3G alternator swap and wanted to know which were compatible parts. My searching points to a 94-95 5.0 alternator, would a 94-98 3.8 alternator swap in the same?

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Yes - any 94 to 99 Mustang alternator will be the 130 amp 3G. However, there are 100 amp versions of the 3G and they are easy to recognize in the yard.


The 130 amp versions and the 100 all have small holes drilled into the front face for breathing. Pay attention to the front face and look at it. There are three "spokes" for lack of better terms extending out from the center. A 130 amp version will have two big holes in each of the spokes, one closer to the center and the other closer to the outside edge.
The 100 amp version will have 4 smaller holes in each spoke - 2 side by side and the other 2 side by side.

Below is a link that shows the differences, look at the front view pictures below the side ones, the one on the left is the case style you are looking for - pic shows the wrong mounting - but the front case holes is what you are looking for

3G Series Heavy Duty Bridge Rectifier High Output Alternator


Also, any 96 to 99 3.8 Thunderbird or Cougar will have the correct 130 amp 3G alternator. The V-8 will have a 3G as well, but the mounting will not work for you.

Also certain front wheel drive mid 90's contours or taurus types have the correct alternator too.

Be aware there are some out there with 8" on center mounting holes - the top ear extends out more, you are looking for the 7" on center mounting holes