Throttle Body problem and question

I bought a new throttle body the other day. After I looked at the one on my 99 XJ 4.0 I noticed that the new throttle body had a smaller bore. More like a taper to the bottom of the throttle body. I am thinking this new throttle body was made for a 2.5liter 4 cylinder. The person I bought it from has a no refund policy. The new throttle body has new IAC and TPS on it. Can I remove my throttle body and clean it and replace the TPS and IAC with the new stuff on the new body? What would you do?

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I would pull your old one off, remove the sensors, give it a good cleaning with both a spray and liquid carb/FI cleaner, then reinstall the sensors.
What was the original problem that influenced you to buy a whole new TB ?

Wanted to see if I could get better gas mileage by replacing my TB. Also takes about 4 seconds to get it to start when the engine is cold.
Will i need to replace the TB gasket? Are those pretty easy to get from auto parts store?

The starting problem of 4+ seconds could be the start of a faulty check valve in the fuel pump, it helps maintain fuel in the system during stops, usually is noticeable after parking overnite. The check vavle is not a show stopper, just a minor annoyance that goes away when your fuel pump goes and gets a new one.
Once you get it back together and get it running do a cold start, turn the key to on for about 20 seconds then go to start, if it fires right up it's the check valve. My 98 cold takes about a 'one one thousand' and it's running, same with the wranglers when cold, when hot, starting is instantly as soon as I touch the start position.
The fast starts I credit with side benefits of Mobil-1 and good batterys. I remember noting the difference when I converted to synthetic oil from the factory oil after breakin.