Sadly your post contains no questions, so I'll comment:
1) I'd start with Google SketchUp. You can take measurements from the Park Ave's trunk, and make a solid model of the space you have.
2) Decide on a configuration. One of our trunk guys can chime in for that... but I'd probably do subs up port up. That way you can use the full length and width of your trunk. How much room do you need above the subs? 3-4" minimum. I'd do 6" if possible.
3) Use the solid model to determine your total air space available.
4) Subtract the space volume occupied by the box walls, drivers, and bracing... then subtract 8 cubic feet (3-5 cf per woofer, is what Kicker recommends).
5) The remaining volume (Total space - occupied space) can be used for the port. I use the12volt.com's port calculator for slot ports, and carstereo.com's for round ports. Use the entire volume available by maximizing the port area, for your chosen tuning 28 Hz to 35 Hz is safe for daily. Use the volume formulas to find the best port by brute force (L * W * H = V) or (PI * R^2 * L = V)
If you need inspiration, check out Moe Lester's box plans. They're well proportioned and don't waste space.
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