Why not rebuilding the existing one or get a similair one from the
scrap?
That is the easiest way.
Erik-Jan.

Since nobody's answered your question, I will try. Nobody makes a "bolt-in"
replacement engine swap kit for your Trooper, unfortunately. There was one
company that sold them, but they've quit selling them, both here in the US
and also in Australia. I know, I checked.
If you're serious about swapping, my recommendation would be for a Chevy V6
or better yet, a 350 V8, but you'll need to change out the engine,
transmission, and transfer case. The making of new mounts, swapping in the
new engine's computer (you won't be able to use your Trooper computer), the
driveline adapters, increased weight, cooling issues, and pump adapters make
it almost not worth it.
I'd recommend rebuilding what you have - and upgrading whatever is possible
from CalMini and some of the other places that sell aftermarket Isuzu parts.
You'll get it done a lot cheaper, faster, and better.
And you won't have a "one-off" model that won't be sellable when you want to
finally get something different.
Hope this helps.
Steve