The Mustang Handbook states to take your intended budget, add up everything you plan to buy and then double that number.. LOL True words... So what's your real budget and timeline??
347 costs the same as 331.. Either way you'll need to spin the motor to get the power you want. That means Gears and a good Cam. Take that gt40 Intake and hook a chain to it and use it for what it's good for.. An Anchor..
I've had a 347 EFI back in the early 2000's. So I know what I'd need. Basically I'd sell this current intake and heads.No one has mentioned the intake - for your HP goals, even a ported GT40 won't is unlikely to get you there with a 302-306. A 331 makes 340 WHP possible (400 crank) with a ported GT40 but you better get professional help with the cam and have the exhaust system to support it. 340 WHP with a 302-306 won't be cake walk, get some good advice on how to get there with the parts you'll need.
Probably go Edelbrock RPM II intake, TF 11R 190 heads and a custom cam. I'd keep compression around 10:5:1 on 91 non oxygenated fuel.
Currently running 3:55 gears, but I think 3:73 would be better. My friend who built my last 347 thinks my current setup needs 4:10's.
Sent from my Moto E (4) Plus using Tapatalk