If you're starting from scratch, buy a set of 6.4 apache heads. They come with a Ferea 5000 series valve factory and can accept a BBC valve spring like a PAC 1520.

$1220 with "core" charge and add in shipping.

Matt Deane in the parts department at Glendora Dodge has a set in stock. I know because I'm considering a set right now...350cfm OOTB with room to grow!

http://modernmoparforum.com/topic/12135-57-61-and-64-hemi-cylinder-head-comparison/

My Build thread: Let the hemi swap begin!

1968 wanna be pro touring whatchamacallit with some fancy stuff and a new roof skin.