[Everett#2390]

340292 "Turbo" Over Counter Angle Plug, 64cc, 2.02-1.6 valves
3767462 327, 62-67, 161/65cc ports
3782461 327, 64-66 Double humpers or Camel hump 161/62cc port
3782461X 60-63, Larger intake runners, 172/64cc port
3991492 350 LT1, 70, 64cc, straight plug, camel hump
3991492 Over counter, strt or angle plug, 64cc, 157/62cc ports

Courtesy of this site;
http://www.kendrick-auto.com/chevrolet_head_casting_number_re.htm

 

[Everett#2390]

Personally, since he's putting it into a '55 and if he wants it to look more authentic/retro, I would suggest the 461X's, bigger ports for 383, and no accessory holes for the '55 era.

Otherwise, I'd run either the 292 or 186.