The original Street Twin uses a Borg & Beck long pressure plate. This is a borg & beck hat with long style fingers. You have lower static pressure and they have c/w on fingers for lock up. It is kind of in between a B&B and diaphragm.
I think they make different diameter overcenter springs depending on static pressure. I would give Brewers a call.

I think a member(71TA) uses the same exact clutch with a Lakewood bell without any issues.