I did a conversion on my steering wheel couple years ago using the TRD
Steering wheel. Anyway don't follow my advice on instructions or advice if you are not mechanically inclined on how to remove a steering wheel. Below are couple of modifications to the steering wheel that was needed to successfully complete the install. Anyway if the hub and harness are the same dimensions it will be plug and play. The threads should line up if you change the steering wheel. I have a Celica Steering wheel with TRD
horn button logo in Red. Let me know if you want it hit me up on a PM or on RJayStyle on my aim. I'll post pics later.
I know this isn't the 6gen but to help out a little the 7gen...
The 7gen Celica steering rod has a notch where the steering wheel lines up. The steering wheel has to fit in this notch for the wheel to turn. It is tightened down by one large nut. Their is a special hub Toyota installs in all it's SRS equipped vehicles which has a black plug built into it well in the 7gen gen it's black. Inside the hub is a coiled white harness (looks like a ribbed harness just like the cable harness made in a computer) for the connections of the SRS and Horn button this harness will allow you to rotate the wheel about 2-1/2 turns if I remember correctly before it comes to a stop without wires being pulled or tangled. Do not take apart the stock Toyota hub it is a pain in the ass to put back together. Just take it off and leave it sealed. This special hub controls the clicks on the turn signal lever so when the hub spins inside the steering wheel it clicks back the lever to the center position turning off the turn signal lights. Without it you will loose the capability to turn off the turn signals automatically and you will have to manually flip it back.
Problems that can happen during the swap.
1. If you have cruise control you will loose it. Unless you can tap into the cruise control wires and relocate the buttons elsewhere.
2. If your hub doesn't fit into the 7gen wheel or the hub is different in size you'll have a problem. Their is a hub that is circle in shape then goes inside the steering wheel right behind the airbag unit. Some people can get away with not having the hub connected. This takes away your use of SRS and Horn. Wiring the airbag with wires ran through the steering wheel will be a pain in the ass goes the same for the horn "remember" the steering wheel rotates. Meaning these wires will wrap around the steering rod either getting tangled, snapped, or shreaded many possible factors can complicate. A proper hub is neccessary.
Steering wheel fitment
3. Steering rod and steering wheels hole diameter fitment
If your rod is larger or smaller in diameter and not the proper size for your new wheel you will have problems. You can try to fix these problems if the diameter is smaller by torqing down the center lock nut tighter. If you have a larger size rod your on your own. I would reccomend making sure the holes diameter in the new wheel be the proper sizes for your swap.
Hopefully you're project will be successful I have seen some old gen Toyota's use the 7gen steering wheel which is why I won't predict it can't be done. When I did my swap I had a problem with the harness "plugs". The TRD
steering wheel did not have the same harness plug to plug into my OEM hub unit since the wheel was from Japan. What I did to resolve the problem I removed the pin in the harness plug and swapped it with the o.e.m plug. That fixed the minor problem. 2nd I had a problem with the horn wire. The horn wire "inside" the stock wheel was screwed in a different location and on the TRD
wheel I had to extend the wire and re-locate it for the Airbag to make clearance and fit.
Anyway with the a correct fitting steering wheel and install all in all everything will go well. On my ride after I did all the usually testing. The alignment went great, SRS works, Turn Signals flip back, and Horn functions. No loss of any safety features. Only loss was my cruise control. Oh well I learned to drive without it. I've got a heavy foot. If you don't have cruise control more power to you! I was going to modify the TRD
steering wheel and incorporate a way to add the cruise lever but got lazy. Why cut and weld a perfectly fine wheel right? When you could just relocate minor things. Hope this helps you figure out some questions you may need to ask through your swapping venture. If you need more help I'll go more in depth with the install but will cut here for now.
Also if you can post pics with your steering wheel taken apart post them up and maybe all of us here can do some type of side by side comparison.