There's an email and they're on FB.

A friend had them make a new flywheel about 3-4 years ago, and both service and end product was excellent. Although I did hear around the same time they preferred to deal with dealers, rather that direct to customers. We did make initial contact via Powermax though.
That was before they started offering clutches though, which the more product they offer sooner or later they will need to communicate easier.

Powermax in Cookstown ( local to me ) are definitely a dealer and I know they've done some custom clutches for them, they'd also be familiar with Sierras, so they would be worth a shout
I did see their clutches at autosport a couple of years ago, and they seemed perfectly fine. ( Link below for phone number, I know there's no pictures.

https://www.powermaxengineering.com/.../66/ttv-racing

Or give Euan at Clarke Motorsport a shout, Xtreme offer a clutch for a Sierra although it probably isnt stocked here.

https://www.xtremeclutch.com.au/en/c...line-catalogue

KFD24019-1B, sprung paddle rater for 480lbft

http://clarkmotorsport.co.uk/

https://www.powermaxengineering.com/.../66/ttv-racing

And this price cant be real lol

https://xtremeclutch.co.uk/product/23263/KFD24019-1B/