If you are looking for a transaxle that is geared correctly for your application and the only trans that will look the part, the ZF 5DS-25 is the only option. I can find you one if you would like to go that route. Expect to pay roughly$12k for one that is RTG. It will be under-stressed at your power level and should last a long time even if you run the car hard.
Hi Urban ... Is the G50 and Adaptor For Sale ?Hi, I have a Porsche G50 6-speed transaxle that is shortened to fit GT40. Also an original aluminium cast Ford smallblock adapter made to fit the Porsche transaxle. More info and pictures can be sent in PM.