Unequal length go from the nearest port on the heads and combine into one tube so rear tube is much shorter than front tube. . Equal length- each exhaust tube on the header is the same length whether it's the tube near the front or back of the engine which makes the header longer but equalizes any back pressure.
chevy runs deep, Don't step in chevy!
67 Coupe 289 - TCI C4 w/2k stall; Holley 4150 570cfm; Performer intake; mild cam; Pertronix HEI; 302 heads; Roller Tips; Hedman Tri-Y headers; H-pipe w/Flowmaster 40's; 9 in posi 3.50; 205/50-17F; 225/50-17R.