Xemeth

Wow it really sounds like nobody here knows what they're talking about.

96-98 and SOME 99 Cobras have aluminum teksid blocks. The rest (GT too) have iron blocks. All 4v's except the automatic 03/04 Mach have a forged crank. 03/04 Cobras have forged everything.

Now OP: To swap 4v heads onto your GT shortblock you will need...

-Heads
-Cams
-Intake
-Valve covers
-COP's
-exhaust manifolds
-fuel rails
-timing cover
-belt tensioner
-alternator
-throttle cable
-throttle body
-coolant crossover pipe
-thermostat housing
-radiator hoses
-secondary timing chain gears
-secondary timing chains
-secondary timing chain tensioners

Now you can use your wiring harness, but you're going to have to modify it. You'll need to extend the wires going to the ECT sensor. You'll need a new connector end for the alternator. And you'll need to change the polarity of the voltage going to the COP's. You'll also need to extend those wires.

Now with 4v heads on a GT block, your compression will be low since the larger combustion chamber in the 4v heads and the dished GT pistons. Now this is fine if you plan on running boost. But if you plan on going N/A you'll need at least new pistons.

Honestly, you don't really sound like you know what you're looking for. I'd just get a complete 4v motor and build it up and put it in.

JC316

None of the Mark VIII engines have a forged crank either.