Ok... i have '65 4v 289 heads that are ported with 1.84i 1.50e valves... i'm running a shelby replica intake full length headers and a holley... i'm running mid 13's... and my car is a little heavier than a falcon
Anyways, my heads cost about $600 complete and assembled after porting with larger valves... you CAN go to 1.94I but you loose power because your chamber has to be opened up... the only benefit you get from keeping the 289 heads is the quenched chamber. A little port work and valves and you have heads that flow pretty damn well. but in the end it's all opinion... actually, MF just did a article on this and they seem to think that you can get very aggresive numbers from those stock heads with port work... just a thought. good luck.
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'63 Merc Meteor hardtop, warm 302, C4 auto, 2.25" Flowmaster Exhaust,
'65 289 heads - ported/chevy valves, performer cam, edelbrock f4a intake, full length hookers, 600 holley, roller rockers, k'n, 10.5:1 hyperutetic pistons... mid 13's hoping to reach into 12's