With the police, depends what you are doing. If you gonna do street racing, yes.
The MOT it's a little more dificult, because you must pass the emissions test and have the wheels aproved in the car documents.
The problem with the wheels, is that Nissan Portugal only approves 18". If you want bigger, you need to make a MOT with an external certified company and then make all the process to legalize the wheels. An bit burocratic process.
To pass the emissions test, that one of the reasons I instaled the AVC-R and the nistune. I can make one map only to pass the MOT, and then change it to the "normal" one.
To buy an cheap 300ZX in Portugal will be dificult. They cost alround 10K-20K. The best thing is to by one with an collision, and then repared it.
In my case, I done that (I bought 2 more 300ZX foreign to take parts, but I sale one motor+trans , one full interior, 4 OEM wheels and some others parts and the real cost for me from the cars are 0 :sorcerer:).
opportunity
http://povoadevarzim.olx.pt/vendo-nissan-acidentado-iid-432379173