I wouldn't know but I'll hazard a guess and say the engine will run just fine with the new head and bigger barrel on the old block, or the whole new engine will run just as fine, on the Bullet ECU and injector. Like the others said on the Bullet thread, the worst that will happen is you will need a Powercommander to optimise it. If that GT engine was near me, I'd be buying it at that price anyway, just to have as a spare. Have at it.