The info I provided is from the master parts catalog.
I always found this to be a very accurate and great source of info.
The 1960 truck shop manual does show different springs between 235 and 261.
However, it also shows specs of the older steel forged 1941-53 solid lifter cam #251 for the 235.
Starting with 1954 PG and all 55 models had cast iron alloy cams, also described in the cam spec section of the same manual.
848 heads were introduced in 1954 with higher load springs.
My 1962 car 235 has the 1954-62 stock hydraulic cam #252, almost identical to the 261 cam lift and duration specs.
A good cam grind for a 235 above 2500 rpm.
Higher lift 235 and 261 motors should have higher load springs and the later pushrods if used above 2500 rpm and especially higher.
Not sure about valve rotators reliability at higher rpm. I don't use them on my engines.
