I have my whole transmission lines done with 3/8 aluminum tube and AN fittings.
If you want to use the factory lines, coming off the transmission and adapter them to AN up near the front of the truck. I would stick with stainless steel compression fitting to AN adapters, since I believe the factory lines are steel and the typical aluminum AN fittings will probably not compress the steel tube with the ferule as well as they do aluminum lines.
Something like this:
https://www.ebay.com/itm/185364203958
Another alternative would be to take your factory lines to a hydraulic shop and see if they can weld/braze AN fitting on the end where you need them.
I MIGHT also trust a high quality Tube Nut and Sleeve like these:
https://www.jegs.com/p/Earls/Earls-H...49390/10002/-1
To install those, you cut your line, slide the nut on, slide the sleeve on, flare the end of the tube to 37° and tighten onto a male AN fitting. But again, you are trying to squish steel with aluminum. I haven't tried it...