When I bought our Syncro Doublecab this past January, it came with BIG
tires/wheels. I took them off even before I took delivery. Today I
finally got around to looking at them.

The wheel is 8 inch wide by 15 inch diameter with an ET 5 mm for offset.
The tire is 225/75R15 102S with 1874 lb. load capacity.

According to what I've read on the List, this tire should not fit. But
it does. What should I look out for to determine if they are safe to
drive on: rear trailing arm clearance, front turning clearance?

I'm not going to drive on them until I'm sure that they are safe.
-Larry