Those (Patrols) are SO rare here it'd just kill me to see a bow-tie under the hood...
I say Cummins 4BT or a Mopar 318 if you really want a V8... Hell the old inline 6's are awsome in my book. Not fast by any means, but they're great off-road and reliable as for sure eh.
EDIT: Oh and you could always throw a Titan V8 or VQ V6 in there. That'd be awesome and very uinique. Also there's the SD33T Turbo Diersel that Nissan made that was available here in the Scout. RPM&O here on the boards has an awesome SD in his Patrol. Seems like an awesome motor with lotes of tuning potential. That'd be a sweet truck for sure if you kept it all Nissan.
I just realized that I used the word Awesome more times then shoudl be legal in one post... that's just...
awesome
Cheers
Dave