My neighbor has an older long nosed Kenworth with a 3406 in it. I was looking for an air leak and happened to notice the ID tag on the injection pump stated that it was for a 3406 pre chamber engine only..
I thought only the "D" series engines were P/C motors. I thought all 3406's were direct injection engines....
Brother in law had a ST 325 Steiger tractor that had a PC 3406 in it. It was a good puller just not enough hydraulics, that wasn't the engines fault though. It was from the 70's.
Bruce P