There is no bell housing adapter for the Peugeot. There is one for the AX-15.
You’ll need motor mounts, headers/exhaust, a car intake and accessory drive, the ECU tuned, plus the adapter for the bell housing. You’ll have a few thousand in just those parts.
Then there will be stuff like the clutch and flywheel, miscellaneous seals and gaskets. Plus you might need to get driveshafts made.
Probably plan for $5k if you can do all of the work yourself.
Whether or not it’s worth it is up to you. I personally wouldn’t pull a good 4.0 for an LS, but if the 4.0 ever has issues, I’ll strongly be considering an LS.