mate, I feel your pain, really I do..we are both pushing our cars ...mine is not yet where yours is but even so it has not exactly been ''painless''...it goes well and I am wondering whether the the FMIC and hybrid are really required...I know myself though I have to push the envelope and finish what I started..! I am just waiting until the car does not have to do 650 miles a week. anyway I digress.
how about a GTA clutch and single mass flywheel? or a JTD performance dual fiction paddle clutch...
honestly I can't believe there is not a clutch out there that couldn't take 300 bhp, its just a question of finding it! a BM 330D m has around 400 odd BHP in stock form..ze Germans are less trouble though.
I wonder if you might get something originally designed for a stage 3 tuned fiat coupe as they push out well in excess of 400 ponies, AFAIK it's a very similar gearbox and has been used as a replacement on some Alfa builds.
Thing is mate I do wonder if going for a different gearbox is a better option..? one designed for more power with a stock clutch to match, again the coupe springs to mind, the 20V turbo had a 6 speed box, it may even work out the same or even cheaper cost-wise...not sure if the ratios would work but its worth considering.
maybe you have found the limit of what can be achieved with that transmission set up safely consistently..I know joel at JTD is meant to be running 272 BHP on his 147 but how many miles does he do a year in that car? one mans reliable is another mans in the garage every week! it all depends on what you need the car to do.
also do you have the quaife yet? as far as i remember not..correct me if i'm wrong...this does make a difference to the reliability of the box and clutch I hear.
funny story that highlights our shared mentality. I bought some really nice brushed ali pedals on Ebay with Alfa logo's ,loveley bit of kit and looked like they might be a pain free fit..
anyway old MOMO pedals off and then offered up the new ones...clutch and brake were a straightish fit, but the accelerator would have required some work to look right, in short all 3 needed some kind of rubber backing to look really good, so I shelved it and have elected to fit at a later date when I have fabricated the required backing material.
anyway I couldn't bear to put them back in the same condition so I got out the wet and dry and metal polish and refurbed the Aluminium, finished on the buffing wheel, I also gummiphledged the rubbers so the pedals now look as good as new again.
that is a frickin study in futility, refurbing something that is designed to stamp all over!
keep us posted on what you decide or possible solutions to the problem.