ported box

That's a dual 2 ohm woofer, and you have two.  How is each woofer going to be wired?

Can you make room in that hatchback for a 7.5 cu ft box?

By using a 2 ohm impedance on one amplifier, that tells me that you are after sound quality more than all you can get out of two amps loaded at 1 ohm each.  That is good.  These subs do handle a great deal of power, so for modeling purposes I used 2000 watts input for the two of them.

You've probably noticed that in the manual the recommendation for one of these woofers vented is 3.5 cu ft (and within the range of 2.5 to 5.0).  But the recommendation of 33 Hz tuning is very peaky in the 40 Hz range.  For all-out SPL, and with little regard for overall sound quality, this may be the choice of many.  It wouldn't be my choice.

For a nice, very flat response you could build a box that is big enough to net 5.9 cu ft after all displacements.  The port has to be pretty large for this woofer due to its parameters (EBP of 53), and will take up some real estate in itself.  Tuning at 22.5 Hz forms a flat response with F3 at about 22 Hz...it will play the entire sub range without any peakiness in itself.  To keep the port at noiseless levels, make a slotted port opening of 48 sq in (such as 4 X 12) with a length of 37.3 in.  Acceptable port noise level can be attained with a smaller port opening, such as 3 X 12 (36 sq in.), instead, if you want to make the port smaller.  At this size, length would be 27.3 in. while keeping Fb at 22.5 Hz.  If intended power level will be more on the line of 1000 watts, the smaller port would be the one to choose.

By adding displacements of the port and drivers, plus the bracing needed for a box this size, the overall size would be up to 7.5 cu ft.  The modeled response looks real good.  Using them in a 3.0 cu ft sealed box is very nice as well.