I was able to id my heads at mortec but the info was limited. The heads are Truck heads as is evident by the term being stamped on them. The code is 3933148 which are Oval, open and with 112cc chamber. Other numbers stamped may be irrelevant but I thought I'd ask: "C 129" ; "GM 4T" and a circle of dots that have a tear drop in the center pointing to one of the dots. The dot pointed to differs for each head. Mortec also says the heads are from either a 366 Truck or a 427 truck. they were on my 66 which came with a 1968 396/325. Can anyone tell me if these heads are ok, if they are high performance, and if I should keep them? Thanks.

3933148 = 366/396/427 ,69 ,2.06/1.77 ,122cc Oval port (large ovals with smaller runners)
C 129 = March 12,1969
GM 4T and the dots are casting line info ,including hour cast.
There not hipo's as there oval instead of the hipo square port.

The tear drop and dots is a clock. The molder would change that hourly and along with the date tag the foundry could keep track of when castings were made. If there was a problem they could know when it happened and could track the problem castings. Most foundries use this system.