I've got this for fuse references, pulled that off of Google:
Wire Gauge------Recommended
-------------------Maximum Fuse Size
00 awg-----------400 amps
0 awg------------325 amps
1 awg------------250 amps
2 awg------------200 amps
4 awg------------125 amps
6 awg------------80 amps
8 awg------------50 amps
10 awg-----------30 amps
12 awg-----------20 amps
14 awg-----------15 amps
16 awg-----------7.5 amps
As for what Nissan used, I'll check my Haynes manual tonight as I can't find a wiring diagram that shows the glow plug circuit on here.