only takes a few minutes to check. But I would think the springs would have a very good chance to have the right install height.
I bet the stock holley springs may even be good enough. Check with holley's website and see what their stock spring pressure is and how much lift they can handle. Going a little light on the spring is better than going too stiff (especially for the break in)
I think the holley heads would make much more power than your old GM heads.