You can. You might need to modify the pickup in the tank that you're going to repurpose. Also, it would be best if you were make a secure method of attaching the return line.
81cutlass - calling Jake. Jake modified his sending unit to make solid connections. He has pics in his build thread for the GP 2+2. Perhaps he can direct you to some photos.
I welded a -6 fitting into the front side of the tank and attached a line inside the tank that directs the return flow away from pickup, but it was a pain in the butt to get the line installed. The next time I do this I'm going to make the entire deal on a plate (4"x4" or so) of flat 12 gauge steel and cut a hole in the front of the tank and have the plate contain the entire apparatus. But you can use the pickup as long as it's at least 3/8".
One issue you need to address is having the pumps staged. Originally, I tried running two AEM380's at the same time and returning through a -6 line. The -6 (3/8) return couldn't handle the flow - I created a small bit (sarcasm) too much fuel pressure and blew the factory plastic truck rails apart haha. The engine ran for about 15 seconds on initial startup and then kaflooey - gas every where
It was definitely a fire extinguisher moment haha.
I believe a -8 return would've resolved it, but I was too committed to the -6 return at that point. And FWIW, I still have the -6 return and stage the pumps. Works great (no kidding). I can see in the datalogs when the 2nd pump comes on via a small spike of about 5psi of fuel pressure and then it levels out as fuel demand goes up. I don't need the 2nd pump on the street because I never make more than a 5 second hit and rarely have the boost turned up on the street.
There are a lot of ways to skin this cat, you just need something that works reliably. Can you attach a picture of your sending unit or attach a link to the sending unit?
EDIT : I missed Duke's Holley solution. That would work great, but be sure to be sitting down for the price I'll guess.