96 cc is typically the best starting point for a street 455. 1971 #96 and 1972 #7K3 are the two out-of-the-box big valve heads with that size chamber. Then you can look at 4X and 6X variants which will need valve and some minor milling work to get there.

The #7K3 heads are reasonably inexpensive, but lack the outer two exhaust bolt bosses which lead to sealing problems with headers. You can use brackets made by Spott's, or you can have a competent shop weld up some bosses and have them drilled and tapped. I chose the second route on the #7K3 heads for my 455.