porting a 350z custom box.

You're not going to be able just to stick a port in that enclosure and make it sound worth a crap. not trying to rain on your parade, but the box just doesn't have enough air space to port it. If you need 1.3 cuft per sub and the box has a total of .88 cuft it's just not going to work. I would look into either building your own box, or using different subs.

A tip to help with the sound to get best effect from the Type-Rs:

Get wood glue and coat the insides of the boxes with it. This will help seal the box better. The glue will soak slightly into the wood and shrink better sealing it. Each chamber is .7cf so you can be generous with the glue. To take up a bit more space and give a seemingly bigger boom to it, stuff about 3/4lb polyfil-stuffing (think cheap pillow stuffing) into each chamber. They'll eat up a little bit of the excess space and slow the waves down for a slightly boomier sound to the Type-Rs. This should get you roughly into the optimum airspace volume.

Ganbatte ne!

EDIT: I take it back... partially... You can port on this enclosure, but there is a good chance for port flaring. (Think wind noise) If you make a port made from a 2" ID pipe that is 8" long from inside of box to end of port in box (Total 8.75" long) you will be tuned at about 33-34 Hz for some strong bass. Do not use poly-fil in this case. The 2nd enclosure is just enough to get a port in there, but do not expect an SPL blaster. But it will give some harder hitting bass around 34Hz

Now then, what amp are you planning to use? I recommend a Class-D mono amp. Most people tend to use 2-channel amps because it's cheaper for the wattage, but nearly all become unstable and heat up (ie, bye-bye wattage) and in many cases, it voids warranty. Wire the subs in serial-parallel form to get a 2-ohm final load. I recommend the Kicker 08zx10001 amp for this or the Alpine MRP-M1000 (if you want to keep it all alpine) for this setup. Both will provide enough power to power-up all the coils at full RMS with wonderful slope control. Personally, I prefer Kicker, due to cleaner power control (from my experience) and high signal to noise ratio (95+db weighted)