the new one is easier unfortunately. there is a kit on z1 but its ridiculously expensive. like 2k for just the parts. I ended up buying the bumper, the diffuser, and a zspeed aluminum undertray (the regular one because i didnt opt to swap to the nismo fender liners). And then i fabricated 2 brackets needed to attach the diffuser and also fabricated the fender liner fillers. Both these parts are $$$ from oem. Zspeed sells the brackets for $40 a pop which is cheaper but it still felt too expensive to me (
ZSpeed Performance Nissan Infinti OEM & Performance Parts). With these parts, you can button it up really well by just drilling a few holes in the undertray.