Can I do this?
 

I have a '66 Mustang hardtop and I was wodering if I could dump a 390 GT engine from the '68 into it. Or is there a better option for maximum power? Thanks for all advice.

I think you will have to cut the spring towers. That's why they engine bay is bigger on the 67-68's.

Why don't you stroke a 302 or better a 351W. Now you can have you cubic inch and it will fit. PLUS !!!! no one can tell the size from the outside. I know you're thinking that you can tell the difference between a 302 vs 351, so can I. But, most people can't. Like Ch**Y people. You can stroke a 351 to 426, I am in the process of doing just that.

Lighter and more power too.

Think about it, no substitute for cubic inch.

I agree, I would not even consider swapping my 351W for any big block. There is no need to, you can get the same power out of a lighter engine.

------------------
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
http://www.mustangworks.com/mustangs...1245-slot2.jpg

If you want big CID, go with a stroked 351W. 392 or 42?. You can get a 392 from Ford as a crate engine with more than 400 hp for about $6000 or Coast High Performance for the 42?. That should be plenty and will bolt in with headers from Heddman or Hooker. Of course you'll need new custom exhaust about 2 1/2".

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

Dropping a 390 into the engine bay of a 66 requires major reconstructive surgery - removal of the shock towers, revision of the entire front suspension etc. The 390 was not a factory option until 67 when the engine bay was made wider to accept it. I totally agree with everyone's advise of sticking with the 302/351 combo in this car.

------------------
1965 K code coupe - numbers matching - restoration ongoing. 1987 LX notch, stock heads and intake, 3.55's and typical bolt on's 13.89@100.25