I am in the process of going over my new Promaxx Big Block heads before bolting them on. Just quick "shade tree" techniques for checking guide clearance, valve seat concentricity and upgrading to beehive style springs and retainers. I'm giving the valves a quick "lap in" because I was able to see a little bit of daylight between a couple exhaust valves and their seats under close inspection. All in all they will be a huge upgrade over my 906's.
If you can see light in between the valve and seat, do yourself a favor, and go have the valve seats cut properly. if you can see light, there is too much run out, and you cant " fix it" properly by lapping them.How do you plan on doing a shade tree ( I understand you are probably trying to save money) runout? Get a good valve job, its worth every penny.A good valve job cant be done without the valve guides sized right as well, it all goes together. My 2 cents.