Adam, here's the real deal, the largest V engine that will fit in a GT without major rebuilding of the car is a box stock 60 degree engine, either Ford or GM. It has been documented that the max horses the rear-end/torque tube can handle is around 200 plus or minus. Anything more, and you'll have to go to a different manufacturer. In order to go for more horses a whole new frame will have to be fabricated for the body to sit on. There lies another problem, the Opel GT is a unibody, which means no frame, although it looks like there is one there. Everything, engine, tranny, front end, rear end all bolt to the body. Without a substantial ladder type frame, excess horsepower/torque will twist the body excessively. There have been instances where the windshields have cracked or been expelled by overzealous throttle applications with large horsepower output engines. There are folks on the site that have put large engines in the GT, but made the transition to complete rebuild of the frames to do it. Yeah, it can be done, but not cheaply, and for darn sure, not by the average do it yourselfer without proper equipment. JMTCW.
i have read all the post like 3 times each if not more. i was just wanting other peoples opinion towards the swap. but i have decided to go with the 2.3L turbo. so i have printed out all of jon haas's information that he has on here and i am in contact with him right now about the in's and out's of it.
The reason for some of the responses is that we all have read, or seen in person, GT's that have been hacked to death by someone who thought they "knew" what they were doing only to discover that the "monster engine' just won't fit, and end up junking the car. Another good GT bites the dust for no good reason! These cars are often butchered beyond repair and hence useless to try to restore. Use the search engine on this site and you will find all you need to know about engine swaps and the GT. And hopefully save another GT from going to the scrap yard. ALL our Opels are a vanishing species. They are never going to be made again so when the last used one is gone they are history!!!
I've been looking at the issues of more power in a GT. The issues range from weight to popped glass with power limitations all over the place. This is why I won't do it myself to a car that looks to be a keeper. Don't forget the weight of the car in general. There is a real issue about rear weight and getting power to the ground.