Do domed KYB 399’s interfere with 302 cast heads?

399 = open chamber, 167 = closed chamber, not saying it's impossible to go the other way around but that's basically what there designed for especially if you want quench, I imagine it would take more machine work to get the right quench out of the 399 then the 167.

Why go to all the trouble to run 167 but not mill the little bit that's needed to zero deck ?

How much power your looking to build will tell what heads to run, cam will tell you want cr to run and those two things will tell you what pistons to run, don't forget about balancing.

Unported 273/318 heads equal around 300 hp with reasonable cr and cam, 360 heads mid high 300's and magnum heads 400 ish.

With porting and or aftermarket there's many ways you can go.