215 six vs 223 6 interchangeability of heads ect.

[Newc]

Hi; I'm looking for comment on any interchangeability between these two 6's. Mainly is the bore spacing different and is the 223 slightly longer than the 215. I drive a 215 '53 and folks are trying to sell speed equipment for a 223. I understand that the 223 has a slightly longer block/head than my 215? Thanks all. I know that this crosses to the late forum. Newc