And here’s the tank, planning on running 10an fitting and feed to the front. Think that should be ok?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.