Engine mounts are fairly easy with a 1JZ, use the existing toyota mounts to make, you just need to remake the top part of the mount to go from the block to the rubber commodore mount, sit the engine in the car, use blocks of wood and packing to get it sitiing in the right place, then use cardboard to make up the shapes need. once you are happy with the cardboard mounts, use these as templates and remake out of 75x6 Flat steel.
If you don't want to go to that trouble I MAY be able to get my hands on mounts made to suit a VR, which should fit the VN.
Only other things to consider is gearbox cross memeber (easy just mod the existing VN item to accept the A340 mounts, tailshaft, I had to have custom front shaft made as the VL required a 100mm extra, also had the yoke modified to accept the standard VL uni's as the Toyota ones are not serviceable ( read throw away and buy new $$$$$$).