You should be able to find a suitable clutch ok. What gearbox are you running? My 240z has a solid centre brass button clutch. It handles over 300hp (at the motor) no problems but is a bit jerky. It's pretty much in or out with no in-between if you know what I mean. Not sure of the brand cause it was in the car when I bought it.
Any luck with your clutch yet?? Try Stonehouse Clutch in Cooee, Shane is very switched on. I recently got a sports2000 off him and a good mate of mine ran a similar thing behind an engine almost the same as yours and it worked a treat, but he ran a L24 flywheel which has a larger clutch and bolt's up to a L20. This is a top secret tip, dont tell anyone ha ha.