I was out of town and missed this thread last week but I'm glad to see you have a choice between two great trucks.
I currently own a T100 and just sold my '85 pickup. I kind of looked at the two trucks like a couple of guns. The '85 was great for short range but the T100 was much better for long range targets. They are both great trucks but for long trips, especially going up and down mountain passes, the T100 is a better choice.
If you're above 5' tall, you'll appreciate the roomier T100. The "extended cab" on second gen trucks is a cruel joke at best. If you outfit your next vehicle for long trips, you could put a fridge in the back seat of a T100. You'll be lucky to get your Camelback in the back of the '86. If the T100 has bucket seats, you just found the best buckets Toyota has ever offered. With the T100 you at least get a driver's side airbag, (but not pass side) which the '86 won't have, if safety is a big issue.
Drivetrains are a draw, can't go wrong either way. I would suspect though, that as the years go by, it will be easier to source parts for a 5VZ over the 22RE. As Scott said, both trucks use Torsion bars and I have no complaints in how the front suspension handles on the highway or back roads. I can't think there is a big wheelbase difference between the two. An extended T100 has a 121" wheelbase and I'm sure an ext cab '86 is around 110". And if you're serious about going Biodiesel, I would think the larger engine bay in the T100 would be an advantage.
My vote is for the T100 based on the criteria you mentioned. It will do more of what you want at this time in your life, with more creature comforts and safety. I couldn't imagine being wedged into an '86 for a 10 hour roadie chugging along over mountain passes. I'd be miserable!
Hope you get to wind up with one or the other! :beer:
......are either of them white?