Most of the issues with an OBD-2 swap are with keeping the check engine light off for smog purposes. The sensors you really need are the crank, cam, map, vehicle speed, upstream O2, intake air, coolant, and TPS. The downstream O2 will help driveability, if you are running a cat-converter, I would install it, too.
The in tank fuel level sensor and EVAP system leak detection pumps are not needed for driveability. It doesn't need the purge valve to run, but I would install it along with the charcoal canister as I don't like the raw fuel smell from the open gas tank vents.
Connecting a brake switch input would be good, especially with an automatic trans, as would the neutral safety switch. The auto trans PCM likes to have these inputs for better fuel economy.
I am attempting to swap a 97 tj engine into my CJ, and I was told that you were the person to talk to. I have questions about exactly what sensors are needed to get the engine running. I don't need a check engine light for any inspection, this is off-road only. I also don't want the tj dash, I plan to run different gauges. I haven't gotten a copy of the FSM yet, but that is my next step. Any insight on the project would be greatly appreciated.
I also plan to run a fuel cell, I have one of those RCI ones from summit. I have a TJ gas tank, and I think it has fuel pump and sensor, but have to verify.