This is some awesome work.
Professional-level fab work along with the engineering skills equals Beretta greatness!
I do have some experience mixing and matching 3rd and 4th gen F-Body stuff with the Berettas. The 3800 T-5 is WAY stronger than the 2.8/3.1 from a third-gen, mainly the input shaft. I used a 4th-gen flywheel and pressure-plate on my GTU's 3800 with a Beretta clutch-disc when I did the 282 conversion. It wouldn't hold the torque, so I replaced it with a Stage-3 clutch set for the Beretta, and the friction-disc was again replaced with a stage-3 Ford 3.0/4.0 Ranger friction-disc for the F40 Six-speed when that went in. It is all very interchangeable, so if you want something off-shelf, just get a clutch-set for the 3800 Camaro if you use that T5, or one for the 3rd gen if you use that one, they all fit the flywheels interchangeably.
Edit:As a side-note, the 3800 F-body cars still use a heavier, thicker flywheel than the Berettas do -about 3/8 inch thicker. So, either space the throw-out bearing closer to the flywheel (which your mod may have already done), or shim the flywheel towards the clutch (or mil-down the bellhousing, but that is too much material to take off). You might get away with less spacing, but be careful. Beware over-extension of the slave cylinder, as the seal will be destroyed from just one time.