I took a little trip through the Mortec site,
http://www.mortec.com/castnum.htm & found:
1. 12506450...87-95...350
2. 376450.....75-81...262/267/305..6 or 7 exhaust bolt holes, 60cc chamber
On the NHRA site with the SS cyl head port vol. it lists the 450 head as a 168 cc intake & 60 cc ex port
The date codes are usually the month first & the day & year next. Like A 23 7 Jan 23 1977 0r 1967 or 1987 You have to know alittle about the decade the head was used in.
Hope this helps you.