In general, the head plate should be at least 3/8" (1/2" is best), tubing should be at least 16 gauge (14 is best).....otherwise leaks and burn-though are going to be a problem as well as the longetivity of the headers.
Cam and valvetrain.....
Given the criticality of the component- IMHO, I don't like speaking to a catalog parts sale person- they really don't know any more about the cam than what they are reading- companies like Summit, while their bulk purchase agreements are great for price, when it comes to making an engine breathe, there are so many variable including elevation, humidity, fuel blends/available octane, most cam mfgs will vary a "core grind pattern" to match the external impactors in addition to the internal impactors- which today IMHO makes the different between and engine that runs well, to one that just seems to run a little bit better, smoother and gets better mileage than expected.
I highly recommend Iskenderian & Crower & Chet Herbert & Lunati...all are family owned, been grinding cams for decades, and both will even re-grind your oem cam if possible- saving you even more $. Isky still to this day inspects/test every valve spring before it leaves the shop!!!!!
I would avoid Comp like the plague............Comp (IMHO) is a mass production (McDonald's type) company which - seems to have experience more cam lobe failures than most and places the blame on the low ZDDP in the oils...then experiences valve spring failure, and it just does a cycle.
With regards to their cams billets, I highly suspect that they are also using Chinese & they do not include Parkerizing their cams unless you want to pay extra for it (Parkerizing is the final step and a crucial step to help break the cam in- a heated acid bath that microscopically etches the metal surface and adds a very thin layer of graphite coating which allows the cam lube to hang onto and penetrate into the cam surface during cam break in) unless you specifically request and pay additional money for it.
This is a not so unusual posting about Comp and their components….. RIP, Camshaft.... - Vintage Mustang Forums