Decide the specification first
Before looking at individual trucks, settle four things: drivetrain (2WD or 4WD), transmission (manual or automatic), body type (flat bed, dump, extended cab) and your ceiling price landed at your port. Almost every later decision follows from these.
Confirm eligibility for your country
Eligibility is a country-level question and it is the one that most often stops an import. The United States applies a 25-year exemption measured from the month of manufacture. Canada applies a 15-year rule. Australia and New Zealand operate their own separate schemes with different requirements. Confirm your own country's position before committing money.
Source the vehicle in Japan
Trucks come from two places: the Japanese auction system and dealer stock. Auctions carry more volume and an inspector's condition sheet; dealer stock can be viewed more flexibly. Either way you should see photographs and, for auction cars, the sheet itself before purchase.
Purchase and de-register
Once bought, the truck is de-registered in Japan and an export certificate is issued. This document, with a certified translation, is what foreign customs authorities and registries will want to see.
Book ocean freight
Roll-on/roll-off is usually cheaper for a single running vehicle. Container shipping costs more but protects the vehicle and allows parts to be shipped with it. Sailing frequency depends on the route.
Clear customs at your port
Your customs broker files the entry using the export certificate, bill of lading and invoice. In the United States this includes DOT form HS-7 and EPA form 3520-1, claiming the relevant exemption code.
Title and register at home
This is a state, provincial or territory level process, and it is where rules differ most. Check your own jurisdiction's current position on kei vehicles before you buy, not after the truck lands.
This is general information, not legal or customs advice. Import eligibility and road registration are decided by the authorities in your country, state or province, and rules change. Confirm your own position with your customs broker and vehicle registry before committing to a purchase.