I don't think you'll like what it does to the synchros, they already can't stand the stock unsprung hub (216mm?) disc's MOI when you're over 4500RPM
some guys use 7.25" ceramic clutches, and mine has a lighter pedal than stock, but a heavy flywheel for a 7.25 is not something you'll find on the shelf anywhere (and you already seem to know that you want as much FW mass as you can stand to run)
Engagement is extremely harsh, I've shattered a few engine and transmission mounts, torn the dogbone mount bolt out of the trans case, broken some (marginal, welded together) axleshafts and forgetting to rev match a downshift will put your head through the windshield. Don't think an o2j's gears or case would hold up to that for very long.
ETA: also, I think they went to a larger starter ring gear diameter with the 240mm clutches, so finding a starter that'll work might be the biggest trouble with fitting a 240mm clutch into the 02j's bellhousing.