Custom. Unless you want a full custom exhaust, you are going to want a hybrid downpipe that is the right "height" and length for the 2JZ, and you want it to terminate where the 7M downpipe would [so you can mate to cat-back exhausts made for the car - direct bolt-in].
I'd say an easy enough way would be to mark in chalk on the underside of the car where the 7M downpipe terminates, then get a cheapo EBay 7M downpipe and 2JZ downpipe.. measure, cut and weld.