[KTL]

Another option is to forego the lock nuts and just use the standard Si-Br nuts with Si-Br lockwashers. That's what i've got. Got them from McMaster-Carr.

But I don't think the Si-Br lockwashers are necessary. You can use standard steel/plated lockwashers since the washers are unlikely to cause any stuck fastener issues, even when they do start to rust?

I'm curious why others use locknuts on the cyl. head connections of the exhaust system? On my 87, the original hardware is standard hex nuts and the inhex barrel nuts. Neither of these two nuts are the locking type. Seems to work fine. Just be sure to use a little antiseize on the studs. The torque spec for these fasteners is kinda low at 18 ft-lbs/25 Nm, so I can see why locknuts might be a good idea. But i've never heard of these connections coming loose? I'm no expert by any means, so take my comments with a grain of salt.