Hello everyone, I need advice. I'm using a 305 from a 1987 IROC in my Model A Street Rod. The guy I bought the engine off of had it in parts, and when I was rebuilding and assembling, I noticed the heads have different casting numbers. One of the mis 14102191, and the other is 14102193. I've been told the 191 head has a 3/8 exhaust and harder valve seats, where the 193 has 11/32 exhaust. My question is, can I use these heads together.......or do I need to start looking for a single 191 or 193 to make a pair? Appreciate the help, Thanks, Ken