Both types of t-stat housings (recessed/non-recessed) were die-cast, not iron.
Hi all,
IIRC, the small letter COBRA intake has a recess for the thermostat. So I would think functionally the non-recess thermostat housing would be best, even if both were used. I would recommend the flush (non-recess) housing.
Also, if you are really serious, these things are date coded, so it will need to be dated prior to engine assembly date.
Cory