Please read if swapping fuel pumps
 

I found out the hard way after recently swapping to a FB270 fuel pump that the rubber seal for the sending unit is NOT reusable. It's states that very clearly on Subaru's parts list and if not replaced it can and in my case did leak.

See this thread. I had several problems too so I feel your pain.

http://www.ft86club.com/forums/showthread.php?t=33993

Also, this is the gasket part no.

https://lh4.googleusercontent.com/-O...0/IMAG0805.jpg

Mine leaked too after filling the car with fuel the first time. It wasn't because I reused it though, it was because I didn't tighten the white lock ring tight enough. I would almost recommend using the factory one the first time, and if you screw it up or damage it, then you have learned your mistake and you can throw a new one in it. I have had mine out 3 times now, and I am still on the factory gasket with no leaks currently.

What's your secret for tightening it without snapping the tabs off lol

I laid a towel over the ring and used a rubber mallet and screwdriver. Also, didn't replace that gasket and haven't had an issues. On/off three times now. Will definitely keep an eye on it though.

I didn't even use a towel, but I used a big screwdriver and a mallet.