Not much for parts in Canada.
You may need to contact some of the US suppliers and wreckers.
Spokane has some good ones.
MS Recycling in Sacramento has Mitsu stuff.

I've done a LOT of welding on my truck, but not for a spring-over. It's a pointless change to make in an IFS rig: How you gonna lift the front that far to level the ride??
The front can be raised by adjusting the base position of the torsion bars (and if you trim down the rubber upper suspension bump stopper), you can gain ~ 2" on the front. Then adding another rear leaf/re-arching/or a combination of the 2 will get you 2" in the rear. All of this will still mostly let you use the stock shock lengths. Spring-over and longer rear shackles will raise the rear, but you will need to get different length shocks.

Not much in aftermarket suspension upgrades as the stock rig is very sturdy and capable as is, and vastly under-appreciated in North America, hence no one wants to make anything for it since no one seriously off-roads them. (tongue firmly in cheek).

These rigs have been SAS'd front and (I'm fairly certain) sprng-overed in the rear. But basically with SAS, if ya gotta ask, ya can't do/afford it.

So, if ya wants it, look to Australia (ARB/EMU), or take up metal fab work.

Body parts: California.

There's a good group of Mitsu's in Calgary and area. Check the deisel board, since some of them used to own what you got.