The t-5 transmission swap is getting popular with the Mustang II however there are a couple choices when choosing a bellhousing/flywheel combination and each has its advantages and disadvantages. I thought I'd take some pics to show some of the differences between them to help you decide which bellhousing/flywheel set-up is best for your car.
These pictures compare the factory 83-93 V-8 fox body t-5 bellhousing/flywheel and 76-78 V-8 Mustang II bellhousing/flywheel and each is catagorized in groups of pros and cons. Note: Either of the bellhousings will require modifying the transmission crossmember when installing the t-5 transmission.
Mustang II bell/flywheel/clutch:
1) If you have a 4 speed in your car you already have these parts.
2) No problem fitting the Hedman, Hooker, or obsolete Blackjack headers.
3) Minimal amount of surgery to the trans tunnel for the shifter.
4) The shifter will end up closer to the factory position even with the factory t-5 shifter base.
1) The Mustang II bellhousing and 10" clutch parts are getting hard to source if you don't have them already.
2) The V-8 Mustang II 148 tooth flywheel is specific for the II and is even harder to find than the bellhousing/clutch parts if you don't have one already or yours is damaged.
3) You have to turn down the t-5 input bearing retainer or enlarge the hole in the bellhousing .010".
4) You have to have a special pilot bushing/bearing sleeve made.
5) You have to shorten the driveshaft.
Fox body t-5 bell/flywheel/clutch:
1) Flywheels and clutch parts are readily available and can be purchased in just about any stage you want from stock to drag race only.
2) Bellhousings are cheap and easy to source.
3) No special pilot bushing/bearing sleeve is required
4) The standard Mustang II 4 speed driveshaft doesn't need shortening.
1) No headers are made for Mustang II/t-5 bell and the clutch fork will interfere. Some have made the Hedman headers work but the clutch cable hits the tubes and you can't put the clutch fork cover on the bell. The factory Mustang II manifolds are said to work OK with the t-5 bell.
2) You have to modify the bolt in crossmember that runs under the bellhousing.
3) The larger diameter flywheel/bellhousing may require you to run a mini starter or at least a late model starter to prevent interference with the engine crossmember although I have seen the standard Mustang II starter used.
4) The post 1981 302 (5.0 liter) flywheels have a 50 oz. imbalance. If you have the factory Mustang II motor it is the earlier 28 oz. imbalance. Your choices are to use the earlier 28 oz. standard 157 tooth flywheel from any Ford car or truck, the aftermarket type flywheel with interchangeable counter weights or use the later model motor with the 50 oz. imbalance. Note: All 289's and 351W's were 28 oz. imbalance.
5) The trans tunnel will require a good bit of surgery for the shifter.
6) With the stock shifter base the shifter will move forward about 3" and be pretty close to the dashboard in first, third and fifth.
OK here's some comparison pics:
The flywheels - The fox body flywheel is on the left. Notice its larger diameter.
And here's the clutch disc comparison. The fox body t-5 clutch/pressure plate is 10.5 inches, the Mustang II clutch/pressure plate is 10".
Here's a comparison of the 2 bellhousings to show how much deeper the Mustang II bell is. This is why the t-5 shifter ends up a little closer to the factory position with the Mustang II bell.
Here's the measurement of the fox body t-5 bell - just a little less than 7".
And here's the measurement of the v-8 Mustang II bell - just a little over 8".
And here's a comparison of the clutch fork position. The t-5 bell is the lower one in this pic. Notice the fork is almost in the middle of the trans mounting bolt holes on the t-5 bell and it's almost directly below the lower left bolt hole on the Mustang II bell. This is where you have interference problems with the headers.
There is also the option of using the 94-95 SN-95 t-5 bell or I'm told there is now an aftermarket bellhousing from Quicktime available but I didn't have either to do a comparison. The Quicktime/SN-95 options are also the least common when doing this swap.