65 roll cage help?

i have 65 cuda i want to cage! i live 3miles from summit racing(yaaah)! they have cage kits! but only go back to 68'. now i know im going to be altering it cuz i want to go back thru the trunk! does any know measurements or if 68 kit will work with tweechn, mostly wandering about the main loop! or somewhere else to purchase?