magnum valve springs?

Does anyone know if there are heavier valve springs for the magnum heads that don't require changing the clips and retainers? I'm thinking the magnum head valve springs are pretty weak to stand up to a non-roller la bottom end. Since almost all magnums are roller I think they went with a lighter spring. My 360 has always been plagued by the sewing machine sound above 3k rpm's and I want to fix it for good.
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