Factory Valve-Spring 'Load Rates'

69 Cuda 440 said
I have used the 'Factory Stock' 340 Valve Springs with the
'Hydraulic' .484" Lift /284* Duration Camshaft.

But that is as far as I will go, and with 3.91 Gears as a 'Maximum' Rear-End Ratio.

That's good info, lock in my memory toolbox.