I don't see a DOHC 3.5 liter V6 engine for mitsubishi
WARNING If any binding is felt when adjusting the timing belt tension by turning the crankshaft,
STOP turning the engine, because the pistons may be hitting the valves.
The valves are spring loaded and that cam is going to want to turn, you have to hold it in place until you get the belt around it, Even if the belt is not around all the other pulleys yet it should help to hold it in place.
You may need a helper to hold it in place while you route the belt.
If you need further help please feel free to post back.