The Resource For All Things Datsun Roadster S211/SPL212/310/311 Datsun Sports Roadster 1959-April 1970 circa 40,000 produced
https://www.311s.org/phpBB3/
The MGB article in the Feb 2003 issue of Grassroots Motorsports doesn't say a thing about resonators. They tested three exhaust systems but there was no res. application. Dang. I'm not sure where I read that. Might have to dig some more. I don't think I could have dreamt up the whole thing. But...for the time being, ignore what I just said. Sorry. The first time I read this, I thought "Woohoo I can put a header on it!" seeing as how it says "downstream of the header/manifold". I think I was reading it pretty optimisctically. Maybe I'm being conservative, but I think that would have to be interpretated that if the car came with a manifold, you have to stick with that manifold. You can change anything down stream from the manifold, but not the manifold. Downstream all you have to worry about is the noise level (the paragraph 3.5 reference).Any part of the exhaust system beyond (downstream from) the header/manifold or catalytic converter, if so equipped, may be substituted provided the system meets the requirements of 3.5. Stainless steel heat exchangers are permitted only if the physical dimensions and configuration remain unchanged. Modifications of any type, including additions to or removal of, the catalytic converters, thermal reactors, or any other pollution control devices in the exhaust system are not allowed and the system must be operable. Replacement catalytic converters must be OEM if the vehicle has not exceeded the 5-year/50,000 mile warranty period as mandated by the EPA. Converters must be of the same type and size and used in the same location as the original equipment converter(s). This does not allow for a high performance unit. If the vehicle has exceeded the 5 year/50,000 mile warranty period, replacement catalytic converters must be OEM-type as per Section 13.