http://www.wallaceracing.com/chokepoint-rpm.php
Calculator for cross section based on rpm
Fun to play with numbers...
A truck motor 4.180 bore 4.210 stroke at 5000 rpm = 2.33 sq inches.
Use a factory 2.05 x 1.30 intake gasket at 2.31 sq inches.
Same bore & stroke taken to 6000 rpm, needs 2.596 sq inches or a Felpro 1233 gasket at 1.180 x 2.200 or 2.596 sq inches.
A truck motor 505 at 6000 rpm needs a SCE #128103 gasket, 2.320" tall.