[Batman]

I know for a fact the GN motor won't fit in an F-body because of the heads. Pontiac made special short heads for the TTA to fit the motor in the F-body, so if you want a GN motor you are going to need the pontiac heads or be prepeared to smash in your wheel housings a little bit. It is NOT an easy swap to do, and it definately won't come in under $5,000.

This is right from the TTA source page

" Some difference exist between the TTA motor and the GN version. Different heads were necessary in order to squeeze the motor between the strut towers. These heads, adapted from the transverse FWD version of the 3.8 liter motor, have the added benefit of improved exhaust flow and combustion chamber design"