The 351 heads will work with your headers, and they will flow more air than your 289 heads. You would want to deck them though so you don't lower your compression ratio. 69-74 351 heads have 1.84/1.54 valves opposed to 1.78/1.45 for 289 heads. I'm not sure off the top of my head about valve sizes in later 351 heads. Just deck the 351 heads and it is recommende that you use special washers (available from edelbrock) because 289/302 blocks use 7/16" head bolts while the 351 block (and heads) are made for 1/2"
------------------
67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Comp. Cam, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.
My 351W Fastback
