I hope you don't mind if I ask - what's a FWD engine?

How does it differ from a RWD engine?
Here's the thing - that G13 in your Samurai is pretty much the same engine as the G13 in my Swift, except that in the Swift it's turned sideways and hooked up to a FWD transaxle - you can unbolt it, and drop it to your Samurai and it will bolt right up, your biggest problem would be the Swift distributor is inline with the engine whilst the Sami distributor is at right angles.
Don't let FWD be a stumbling block, the engines themselves aren't significantly different.
The popular swaps are the other Suzuki G series engines - the G16 from a SideKick or Tracker or maybe a Baleno/Esteem - it does require an adapter plate to bolt up to the Samurai transmission, but it's a fairly common swap and I think there are kits available.