I think it depends on the intended approach to bypassing border security. If you're trying to slip through a custom's checkpoint unnoticed, then as Kirk touched on earlier, trying to remain as inconspicuous as possible is key. A common model cross-border commuter vehicle, like a Gaz, with minimal modification. A shielded smuggler's compartment and nothing else would be best. Also, I would try to have a legitimate cargo to carry across, or at least have a record (true or falsified) of having delivered a cargo with your cover being that you're returning from said delivery.
Now, if you're trying to avoid the border patrols and sneak across the border, I suggest a Shin-Hyung with a Level 2 Amphibious Operation Package, Level 1 Ballast Tanks (most GM's accept that Lvl 2 Amphib allows your ground vehicle to count as watercraft. If they argue, point them to James Bond's Lotus in The Spy Who Loved Me) and Level 2 Life Support. I'd also recommend a Manual Control Override, so you can run the vehicle's electronics "off-line", rather than trying to spoof your way past automated node searches with a stealth program. I recommend the Shin-Hyung because it still gives you plenty of room for other modifications for your shadowrunning career. Then it's simply a matter of following the Green River which flows from the Cascades to Downtown Seattle. Remember that most watercraft aren't equipped to detect and trace submersibles, and this goes double for "brown water" security.
