Valve Lift Stock 5.7L Early Stock 6.1L Stock 6.4L Edelbrock
.100" 71 80 86 82
.200" 134 161 168 165
.300" 192 227 239 251
.400" 233 270 292 308
.500" 256 289 315 335
.600" 258 294 323 345
.700" 261 296 324 348
Their Flow Numbers .

As for a Dual spring, looks like the spring seat area is 1.55 as delivered. FWIW.

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