Same thing happened to my dato 1600 which had an fj20t in it...this is going back to 1998.
The car was found and stripped like your gtr, the guy was unemployed so legally I couldn't get a cent out of him and as my solicitor explained "its like squeezing blood out of a rock".
To his day he still owes me 8k but I decided to let it go after a few yrs as it is no worth putting my family in potential danger, i would retaliate much harder which isn't a good thing.
I got my car back minus the pieces as they were sitting in his house. The issue was that I couldn't prove those bits were mine + the numbers were already done on the chassis and block so I had to identify the car with 40 unique markings prior to seeing the car again - I noted over 100 markings.
Our law sometimes protects the thief more than us.