Toyota advises to shift the trans in 4th gear and shift the rear t-case into netural. This stops the trans from spinning dry and cirulates the oil in the t-case so the bearings, gears, and shafts will not fail, but the front driveshaft now spins all the time. This is not good. I have seen many front driveshafts come apart at high speeds.
Towing the Marlin dual case in netural, and the rear case in 2 high will circulate the oil in the rear case, but the cage bearing on the front input gear will starve for oil.
Towing in; trans-netural, Marlin-high, and rear case-2 high, will starve the trans main shaft cage rollers for oil.This can be done for short trips-less than 5 miles?
To play it safe, remove the rear driveline (best), or get a rear axle unlocking hub kit from Brian at Front Range Off Road (good but cost $$$$ and adds weak links), or leave the engine running in netural, Marlin in high, and the rear case in 2WD (would work but risky).
After all this explaining, I have a customer that towed his 4x4 truck behind his motorhome in netural, and the Marlin in high, and the rear case in 2 high for many, many miles with no problems
Marlin