I've wanted too do it with my 165 for years. I've actually started prepping it, it's in my shop completely gutted and maybe a quarter of the stitch welding is done on it. About a month ago I went halfs on an ex AE86 rally car with a buddy. It had been rolled and had no motor in it. We did the body work on it and built a motor for it.
It looked like this when we got it.
Here it is after we were done with it.
We just got back from Rally Idaho last weekend. The car was awesome, except for some minor gearing issues and it needs a retune (we're running a non TVIS motor on a TVIS computer, so no low end) other than that it was extremely predictable and pretty quick above 4500. It made me think twice about rallying the alltrac. We only spent $1300 total on the AE86, I don't even want too think about how much the alltrac is gonna cost.
I would try and find a cheap 2wd car to start out with so when you roll it (you will eventually), it won't matter. Race that for a year or so then decide if you want too rally the alltrac.