Does anybody know why Chevy used the earlier 913 heads occasionally on the 58-62 235 blocks for passenger cars?

I have a Feb'1958 cast of that head on a 1962 block and am about to put an 848 on instead.

Just curious to find out why some cars had the lower compression head.


On the road every day...
1952 Truck - 235
1948 Coupe - 261