Note: I'm posting this now, by popular demand, but will be adding more later specifically the small hoses around the throttle body and the ever-imposing Achilles hose, aka "Hose of Death" ... and also the bulk hose lengths for 2WD after I've verified them ... stay tuned! -- Gwen
All vans, manual transmission
GREEN arrows are radiator flow (sorry, lower hose not shown but if you can't find that on your own ... well ... this is not a job for you!

Part numbers:
lower radiator hose (2WD) 16572-71010
lower radiator hose (4WD) 16572-73040
RED arrows are heater lines
Skylervan, 1989 DLX 4WD is the one modeling the nice new hoses.

Here the coolant leaves the engine. Note the separate cast fitting for the heater lines. In vans with no heaters (according to Toyota), the fitting is present and capped off.
Part numbers:
green arrow
upper radiator hose (2WD) 16571-71040
upper radiator hose (4WD) 16571-73050
white arrow
radiator breather hose (2WD) superceded to 99556-10460
radiator breather hose (4WD) 99555-10500
blue arrow
hose to reserve tank (2WD) 90099-33393
hose to reserve tank (4WD) 85338-73010
red arrow
hose, heater water inlet, A (2WD) 87245-87014
hose, heater water inlet, A (4WD) 87245-95D09
plug (cap for vans without any heaters at all) 90339-16007, superceded to 90339-16001
Now, peering into the darkness, that heater hose goes to a pipe that has a tee off it for the rear heater. Vans without a rear heater may have the rear-facing tee capped off.
Front heater lines, looking toward the radiator where the pipes appear and disappear around on either side:
Part numbers:
hose, heater water inlet B (2WD) 99556-30500 L=400
hose, heater water inlet B (4WD) 87245-28050
hose, heater water outlet A (all vans) 99556-30980 L=820; superceded by 99556-31000
Layin' on yer back looking up (the front bumper and your feet are "down" in the pic):
Part numbers:
hose, heater water inlet, E (2WD) 87245-28010 this part is NLA!
hose, heater water inlet, E (4WD) 99556-30500 L = 390
NOTE: This van came to me with the aftermarket tee, presumably to backflush the heater core. The hoses do not bond with the plastic of the aftermarket tee AND the plastic is subject to cracking over time from the hot coolant, and that means eventual leaking. I had to eliminate the tee and can't recommend them.
Looking up from behind the driver's side front wheel, the heater coolant heads for the mysteries inside the block. Note the itsy-witsy pipe tee coming down from the throttle body regions; there's a li'l hunk of 8mm hose attached to it (not visible in this pic). For vans with no heaters at all, the 5/8" end of the pipe is capped off, allowing the coolant from the TB a path back to the engine.
Part numbers:
hose, heater water outlet, E (2WD) 87245-87016
hose, heater water outlet, E (4WD) 87245-95D08
plug (cap for vans without any heaters at all) 90339-16007, superceded to 90339-16001
Let's tour the rear heater coolant path now (a reprise of pic 2, leaving the block and heading for the tee):
Looking up from behind the passenger side front wheel. The black-in-a-white-balloon asterisk is a bolt for the return pipe (more on that in a moment).
Part numbers:
hose, rear heater water inlet, A (2WD) 99556-20490 L=430; superceded by 99556-20500
hose, rear heater water inlet, A (4WD) 87245-95D15
hose, rear heater water inlet, E (2WD) 87245-87026
hose, rear heater water outlet, A (2WD) 87245-87026 (note: same as above part)
hose, rear heater water inlet, E (4WD) 87245-95D06
hose, rear heater water outlet, A (4WD) 87245-95D07
Looking directly under the van from the driver's side. Two more black-in-a-white-balloon asterisks mark the other two bolts holding on the return pipe. To get at the nassssty upper hose clamps for the little rear heater core inlet and outlet, remove these three bolts and the hose clamps and lift out the whole pipe and pair of li'l hoses. NOTE: This pipe CAN be replaced with 1/2" bulk hose and zip-tied to the same spots if/when it deteriorates; just add the pipe length to the lengths of the "hose, rear heater water outlet, A" and "hose, rear heater water outlet, E" above ... ie, one long hunk of 1/2" heater hose (secured to the tubing that the pipe is bolted to, of course).
The pipe itself is discontinued.
If you remove one of these pipes in good condition (such as when eliminating the rear heater and lines), be sure to offer it in the For Sale Parts and Accessories portion of the ToyotaVanTech.com forum!
Looking up from behind the driver's side wheel again, the rear heater line joins the pipe returning from the front heater. No rear heater = cap off this tee.
Part numbers:
hose, rear heater water outlet, E (2WD) 99556-20300 L=280
hose, rear heater water outlet, E (4WD) 87245-95D12