There are alot of choices when swapping engines into minitrucks. 350's are probably the most common, then I would say 5.0's. I don't know of any Mazda swaps but I'm sure with a little patience you can find all of the info you'll need.
A short list of the things you'll need are:
All new mounts and brackets.
New radiator.
Transmission and mounts.
Possibly an entire new crossmember, or at least a heavily modified stock one.
Custom headers may be in your future to fit around the various obsticles in an engine swap.
A way of running it; ie. a full wiring harness and ecu, or a standalone.
A way to run your stock guages. Unless you want to shell out more money for that.
The trans tunnel will most likely need to be at least beaten out at the very least.
All new fuel lines.
All in all there is ALOT of custom fabrication that will be needed and plenty of time. If you rush things during an engine swap then it doesn't turn out anywhere near the way you planned.