Maxum 101
I'm not sure about the 402 headers or specifically what they are. But the "Z" heads do need a header that is different from what SPF supplied a few years ago. The original SPF SBF headers were for a rectangular port that was not vertically centered around the bolt holes. I know that SPF has made changes over the last few years with a few improvements to the exhaust port to header mating.
The Firefly "Z" headers are not cheap but they are a great design.
http://www.fireflyperformance.com/ Ron builds SS sidepipes and headers.
Jim 1855