Well To Start Off, Hope I'm Finally In The Right Place, I Have Accounts On A Ton Of 1969 or Classic / Vintage Mustang Forums, I Asked Them So What Would Happen If I Were To Take Out My 302 Small Block For a 390 4V FE Big Block, And What's The Difference Between a 360 and a 390 (I Was Originally Planning on Swapping a 360 / 390 That The Owner Claimed Out Of a F350 So I Figured It Was a 360 And I Decided To Go For An Original 390 S Code) Everyone Told Me That There Horrible To Put Performance Into And They Cost Way Too Much, Just Build a 351W or Your 302, But That's What They Suggested, I'm Still Sticking With The 390, I'm Going With a Detroit Speed Aluma-Frame With The FE Mounts So It'll Clear It Plus It Deletes The Factory Strut Towers, My Question Is If I Put a 390 4V, Do I Have To Modify My Original Gas System, Because I Was Originally Planning On Putting a Fast EZ Efi System On It Anyways, Also I Really Don't Want To Bore a Motor, Is It Neccessary (Sorry If It's a Dumb Question) But I Wanna Stay As Close To Original As I Can, But Knowing That FE Motors Weigh 100 Pounds At The Least Then a Small Block Aluminum Heads and Intake, I Wanna Put Aluminum Water Pump, Intake, Heads, Etc. Any Advice or Ideas On Where I'm Going? Thanks