There is no doubt in my mind that you could build a 360 with flat tops, the TF heads, a decent sized cam, the TF manifold, and nice headers....... and easily make 500hp.
You could do the same with RPM heads that have been worked over........ but after buying the RPM heads and having them reworked....... it would have been cheaper to just by the TF’s in the first place.
I’ve tested a 419 with RPM heads I ported at 585hp........ and I don’t get anywhere near the numbers out of them that plenty of others get.
I feel that 600hp from a bracket race type stroker build would be “no problemo” using the TF heads.