Valve spring selection on a non-high-performance engine is pretty simple. Pick a spring that doesn't "stack solid" at full valve opening and has enough seat pressure to prevent compression/combustion pressure leakage when the valve is seated. It's difficult to imagine a stovebolt engine operating at an RPM range where valve float would be an issue, and compression pressures sufficient to cause a leak past a seated valve are almost impossible due to the huge combustion chamber volume, even on an 848 head. I think the Corvette springs that match the cam would be an excellent choice, or pick any spring that comes close to the same specifications. A good valve seating job and proper guide clearance is probably a lot more important to good performance than getting picky about valve spring specifications.
Jerry
