I think the only way to ensure you get an LFP at this point is to buy one from existing inventory. And the best way to do that is to get on the Discord where all the new inventory cars are being posted. Set up notifications for your state (and maybe surrounding states), and act quickly on the car you want.
ABRP is great, and was a big help for me too when I was deciding whether an SR+ would have enough range for me. And for what it's worth, I did my first 114 mile round-trip commute in my SR+ LFP yesterday. With all the talk about how you should only expect to get 80% of the EPA range, the fact is that my trip to work (which is net downhill) I got 102% of the listed range, and on my way home (which is net uphill) I got 97% of the listed range. I left home with a full charge showing 254 miles, and 57 miles later the car still showed 199 miles of range left. That was mostly doing 60-75 MPH on the freeway. To be fair, I was in Chill mode and the weather was perfect. But I did have the HVAC running some, it showed me that if you drive the car conservatively you can get the advertised range, or even a bit more. Eliminated any range anxiety I may have had.