Have a 509 with iron heads Merlin 320 hvh intake and 850 qf Looking to upgrade the heads to aluminum ones thinking about dart pro 1 not sure with size 310 or 325 runners any input would be great or suggestion on one you are using

Personally with a 509 NA engine I wouldn't go much larger tthan 310-320 runners. I wouldn't recommend out of the box heads regardless what you run. Porting gains are huge and setting up heads are crucial. Dart 310's are good heads but lots of choices now a days. If you don't plan to port I'd probably look into afr 315 cnc. Their 300 magnum are excellent flowing torque monsters also. Single or twin app and under 6k rpm I assume.

I had near same cam specs 244/248 with 310's on 496's. Advanced 4 deg. Peaked at 5,800.

My motor build will not set the motor passed 32 if I move it he will not stand behind the build

I think gitrdun meant where the cam was set, at 4 deg advanced. Not ignition timing.

Lol sorry yes it is

Will he stand behind the exhaust valves and seats when they leak like siev after 100 hours?

everything within reason after 100 hr which is 3 seasons I wouldn't expect him to eat something like that but advancing the timing will lead to burnt holes in pistons or meltdown issues extremely fast if you don't adjust fuel mixtures and run high-octane fuel pre-detonation etc. etc. high-octane fuel's on the water by us are very very limited and at four dollars a gallon not worth it