Depending on which model # head and the REAL conditon of the heads you have they will be fine for a mild to pretty warm build. They are not race heads and some guys I've read on here say they are "junk"....not so.
I had a pair of #60899 heads on my 331" sbc and they performed very well. If they are 64cc heads make sure your compression won't be too high (with your pistons) for the street. Iwould have them checked before you install them, just never know how they were used prior to your purchase.