Here is one for I think a decent price. https://www.ebay.com/itm/Chevy-Impal...IAAOSwW1Bdvdov

And you'll need one of these as well https://www.ebay.com/itm/Small-Block...8AAOSwsptbzhCn

These are nice as well but a bit pricey, stay away from 55-57 valve covers as they have staggered mounting holes and the only heads from that era that are wotrh anything, IMHO, are 57 Fuelie heads that are very pricey if you could find a set.
https://www.ebay.com/itm/1959-1967-C...EAAOSwWahdfEfK

Good luck and thank you