You'll have to fly DTW-NRT/NGO/KIX or MSP-NRT; and WBC seats on those routes are hard to get, even for elites! LAX-NRT is operated by a B742 but with the old WBC seats. You could try ORD-AMS operated by KL. Within Asia, you could try NRT-MNL, NRT-HKG, KIX-TPE, NRT-PVG, NRT-GUM, NRT-HNL.
Don't forget that KE and MH also operate flights with B747 equipment. I know MH uses a B747 for LAX-TPE-KUL routes and KE uses B747 equipment for JFK-SEL and LAX-SEL.
Other than using mileage-based upgrades, the best way to get up there is to work for an airline

or buy a ticket from a consolidator. Some cost as "low" as $2500.

But when published fares are around $6000-$9000, $2500 isn't bad.
- Pat