I'm not sure what I've done is generally accepted practice, but I've been trawling eBay looking for a Thema 16v Turbo clutch kit, and finding stuff in the £150-£200 range. Which is OK, as I'm intending to use a VX 228mm flywheel with a Thema 16v Turbo clutch on a carb 2000 Beta with twin DCOE 45s etc. If I can get 155-160 bhp out of that setup I'll be very happy, and I'm confident that the torque of a n/a 2000 motor won't be anything like that generated by a Thema 16v Turbo's spiky output.
However I've recently noticed in separate listings an LUK 228mm clutch housing for VX, Thema Turbo 16v and Alfa 164, and a pressure plate (AP in this case) for same. And both were going for about £25 inc. postage. So I took the gamble, have received the pressure plate and am awaiting the clutch housing. I already have a NOS Beta clutch release bearing. I realise this is a bit of a gamble, but it's one I'm prepared to take. And as a Thema Turbo 16v clutch should be well over-specified for a carburetted 2000 Beta, I'm quite happy with that choice.
One thing I have noticed is that clutch kits for Alfa 164 3.0 engines are the exact same fitting as Thema Turbo 16v units, but are always priced substantially lower. Why should this be?