Just found this:
V6 to V8 swap FAQ- Newbies Read Here First!
Ok, so you're wondering about a V6 swap in your V6 mustang? Read this FAQ first. Then SEARCH this forum and Google. If you still have SPECIFIC questions, post them up here.
1. Can it be done? - YES, but it's a LOT of work. I've only ever seen a few swaps completed vs a hundred times I've seen it asked about. It's not something you will be able to do in your driveway in one weekend. It's not something for a teenager to do by themselves on their first car... unless you're some sort of mechanic prodigy LOL.
2. How much will it cost? - Anywhere from free, to $1000 or more. Free being possible if you buy a totalled car and part out what you don't need. This will depend on how much you pay for the car itself, and what you can sell on it. If you decide to buy everything separately; the engine may not cost much, but all the little odds and ends will quickly add up to more than your original estimate. A "donor car" is by far the best way to go. That way you can have both cars next to each other, and just take everything out of one car and put it into the other.
3. Can I put XXXX engine in XXXX year car? - You *can* do any swap, but it will make everything a lot easier to stick with a setup that was offered as factory for your year. This way everything will be plug and play, completely factory, no fabrication or custom re-wiring necessary. Custom wiring can quickly turn into a nightmare. The 5.0 and 4.6 K-members are different not a perfect fit if you were to try to swap. Brake pedals differ between 5.0 and 4.6. Fuel systems changed on various years.
4. But I can get a running XXXX engine for only $100 bucks. Can I still put it in XXXX year even though that engine was never offered as factory for my year? - You're on your own buddy!
5. Can I swap from auto to 5 speed at the same time as the engine swap? - That would be the BEST time! You will already be 2/3 of the way there. Basically, the only extra work is to swap pedals and swap shifter. Use search for the specifics. It's been covered many times in the V6 and the V8 forums.
5. What parts will I need to swap? - The short answer is: The engine and related components, the exhaust, the computer and all engine wiring. If going to 4.6 you will also have to swap transmissions, and brake boosters. K members are the same for GT and V6. 94 95 3.8s had motor mounts to fit the 5.0 crossmember. In 96-04 the 3.8s got different mounts to fit the 4.6 crossmember.
6. I can't get a donor car. What parts will I need to get separate?
ALL 94-04
Rear end: Optional. Some V8 guys report beating on the 7.5 rear for years, while some V6 people report breaking them. A 94-98 GT rear will be a direct swap for 94-98 cars. A 94-98 car can also use a foxbody 5.0 8.8 and it will bolt right up. All the axles and brakes and everything from the 94-98 V6 7.5 rear will swap right over to the Fox 8.8. 99-04 cars should use a 99-04 rear because they had wider axles and wider housing than 94-98.
94 & 95 3.8 to 5.0 - All parts listed are 5.0 specific unless noted.
These cars have the least to swap
Complete engine - pan to throttle body
Throttle cable
Air intake
MAF is the same and can be reused
Engine accessories w all brackets, lines, wiring, hoses (accessories themselves should be the same for 3.8 & 5.0)
Motor mounts
Complete exhaust
Radiator & hoses
Fan
Overflow should be the same
EEC with harness
All engine and trans wiring harnesses
Dash harness (?)
Speedo cluster
CCRM (constant control relay module)
Transmission, driveshaft, and starter from the 3.8 can be reused on the 5.0.
Auto trans will need 5.0 flexplate from 87-95
T-5 trans will need 5.0 flywheel and clutch from 87-95
T-5 will need to swap to a 94 95 5.0 bellhousing. The 3.8 and 5.0 bells have the starter in different positions to accomodate the different diameter flywheels. Fox bellhousing will not work because the 94+ T-5's input shaft is longer than fox.
96-98 or 99-04 3.8 to 4.6L - All parts listed are 4.6 specific unless noted. Use parts from the sub group your car is in; 96-98 or 99-04
Complete engine - pan to throttle body
Throttle cable
Air intake
MAF
Engine accessories w all brackets, lines, wiring, hoses
Motor mounts
Complete exhaust
Radiator & hoses
Fan
Overflow
EEC with harness
All engine wiring harnesses
Dash harness (?)
Speedo cluster
CCRM (constant control relay module)
Hydroboost brake booster with all lines - the vacuum booster is too big and will not clear the 4.6
Transmisson - You need a 4.6 transmission. They had 4.6 specific bellhousings built into the case..... even on the manual transmissions.
Flywheel and clutch for T-45 and 3650 manuals
Flexplate for 4.6 auto trans 4R70W
Driveshaft - 4.6 has a specific yoke that is not the same as any 3.8 yokes. Tubes are the same length, in case you want to swap only the yoke.
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I am sure there are many other small details that will come up for anyone doing this swap. Any corrections or helpful info, feel free to post it up!
