Forget about 100% legal importation of a post-1987 70 series into the US, regardless of drive-train, because the vehicle doesn't meet DOT safety requirements. Period.
Quasi-legal, "gray market" importations can and do happen all the time, there are many loopholes at the state level and a couple still available at the Federal level that people take advantage of (not advocating this in any way). Methods vary from "close-to-legal" to "extremely shady", or infinite shades of gray (market). If you're doing this for a one-time importation and know you'll keep the vehicle forever, it's actually not too difficult (depending on the state you're located in), but you have to learn to live with two realities:
1. If you ever get caught (even if you likely won't), you could be in a heap of trouble, or at the very least, lose the vehicle and pay a hefty fine.
2. Because of the shady importation, the later sale of the vehicle will be extremely difficult, so the overall value of the truck will always be questionable.
If you're cool with both of these points, *DO YOUR HOMEWORK*, there are methods available. And if you decide to go this route, be corteous and don't ping those who have gone before you, most people don't like to talk about it unless they know you well and trust you.