1972 Demon with 71 340 casting

I wasn't around "back in the day" but I can tell you a 2, 3, or even 4 year old block may get built into a current engine in today's OEM world. It has to do with how engines are expected to be needed and if sales don't support the projections, then the casting run of blocks sit around waiting to be consumed until another batch is made. I won't name RPO's but this is common for the lower volume engines today.