In this case just use the stock V8 Flexplate which is 164tooth.
94-95 5.0L 5spd: 157tooth Flywheel
94-95 5.0L Auto: 164tooth Flexplate
94-04 3.8L 5spd: 164tooth Flywheel
94-04 3.8L Auto: 164tooth Flexplate
As you see this is why you can mount a V6 Auto behind a V8 with no modifications but when you want to use a 3.8L Bellhousing you need a different flywheel. Because the 3.8L bell is made for a big flywheel than the GTs.
I knew there was some difference between the 5.0 and 3.8 bell. Why would they put a "5.0" stamp on them if it was the same as a 3.8?