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Discussion Starter #1
My car is a 1990 Cougar LS with 3.8/AOD

I want to swap it for a 87/93 Mustang 5.0 with emissions and accessories.

I want it to be as "factory" as possible (as if the car came with a HO)

Will my AOD be good? Is it the same as the Mustang 5.0 AOD?

What should I use for the computer and wiring harness?

What about dual cat mid pipe and dual exhaust?

This is just a cruiser, not a hot rod.

Like to keep things cheap as possible, but do a nice job.
 

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You'll need a 1991-1993 5.0HO MN12 for donor to make it easy, might as well use that motor (the 97-93 Mustang 5.0HO won't quite fit, but the 94-95 does, because it's the same motor)

Well, the MOTOR fits, but the intake and the accessories don't quite fit the hood line.

From what I understand (please correct me if I'm wrong, people!) the 3.8 doesn't use the same bolt pattern for the bellhousing the 5.0 does, so you'll need a 5.0 AOD also. However, the Mustang tailshaft is a different length, so to use that, you'd either have to have it modded to fit, or use a custom made driveshaft. Again, using a MN12 5.0HO donor, that's taken care of.

Using the donor, you could use the donor wiring and computer.

Do remember the 1990 didn't have the 5.0HO available, so it won't quite be factory no matter what you do.

As to the exhaust - the're the same from after the third cat (one part number in the Walker book for the Y pipe back for dual mufflers), so that's not a big deal. Again, with a MN12 donor, you can use its front pipes. As far as true duals, check MandrelExhaustSystems.COM for their offerings.

RwP
 

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The 3.8 and 5.0 do share the same bell housing, but the 3.8 got a weaker AOD, and even the stock 5.0 AOD is barely enough for a stock motor in an MN12. The 3.8 trans will work, but not for very long. Easiest way, like Ralph said, is to get a 91-93 5.0 tbird or cougar donor car. With that, the swap will be direct bolt-in and plug and play. Trying to use the fox body wiring harness will result in lots of time spent wiring, and extra cost, so just keep an eye out for a wrecked or rotted 91-93 5.0 MN12, and save yourself a lot of aggrivation and parts chasing.
 

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Discussion Starter #4
Thanks guys!

I wasn't aware the 91-93 mn12 came with HO option (thought it was a standard 5.0)

That sounds like the ticket.... recalculating my salvage car search!
 

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Discussion Starter #5
Oh, one more question...

Any pitfalls with the digital dash in my 90 Cougar?

Will it function properly once I swap in the 91-93 mn12 ECU, harness, 5.0?
 

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Oh, one more question...

Any pitfalls with the digital dash in my 90 Cougar?

Will it function properly once I swap in the 91-93 mn12 ECU, harness, 5.0?
Ideally, you get one that had the "disco dash" so it's all copaseptic.

OTOH, you can add the extra wires to the harness from the donor. Don't know if the support is automatic, or if you'll need an update (a "tune") to use it.

RwP
 

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The other option is to just hunt down one that is totaled and buy it it has everything you need. Search craigslist all around your area. Cause even if you have too tow it 150 miles it's still cheaper than buying here and there. Plus this greatly improves your changes of a "JACKPOT" find. I paid my buddy 20 bucks and rented the car trailer for my sc, it took me 12 years to find it but it was worth it.
 

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The digital dash will work just fine with the 91-93 5.0 ECM. You will just have to use your dash harness, and there will be a few things that need to be re-pinned to make everything work right, but a bit of time with the wiring diagrams for both cars and you should be able to figure it out.
 
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