cylinder head question?/AGAIN

Well, yea, it is easy, to a degree. Lets not just throw parts at something and expect magical numbers to pop up. Your also listing a 100 HP difference. That's nothing to toss around like a HP gain from a dirty to clean air filter.

I don't know about the 250 head. I'm also not sure exactly what it is your looking to do...exactly. Given the engine size (Via bore and stroke) it should be easy to get 400 HP with basic good rebuild work and a set of higher compresion slugs. Unless your current ones fit the bill.

Now these ported heads. Valve size is important along with what exactly they did for the porting work. If you find these heads with a full port job and gasket match along with bigger valves all around, they won't work to well with a Hwy. or modest gear ratio and/or a small cam.