NPT + your choice of An
I got mine with straight-in NPT fittings. I could then order up any assortment of inexpensive (except banjo) blue AN fittings with the appropriate NPT fitting on one end. I used 90 degree elbows for all ports. You can put the Andair fittings into the valve without screwing them down (snug fit, you'll be surprised) to get the NPT elbow fitting in and tightened, then you have four possible orientations. Once you're happy, insert and tighten screws, then make the anti-rotation dimple beside the screw heads, according to the directions.
Since I used the duplex valve, this was handy. If you're using the single level (left, right, off, feed section only, no provision for return), then I think you can make it work pretty much any possible configuration, including the Andair 90 degree fittings.
Yes, standard IO-360 with AFP injection you could run a single return line straight to a tank, or even t'd into either tank's feed line on the tank side of the selector valve. As I understand it, a typical purge could transfer a quart or so from one tank to the other. Unless both tanks are already venting thermal-expanding gas, you shouldn't spill too much.
Want to be sure? Don't take my word for it. Find out which FI system you'll be using and give them a call. I did. Ask what they recommend. Call your engine manufacturer if you don't know which system it is.