I ran a BossEFI for a number of years, but didn't come to a happy place with respect to tuning. Their mapping software was pretty quirky, and then the company got bought by Professional Products. I now run a carb but I still have all the EFI gear... Might put the throttle body back on with a different controller at some point when I have time to play with it.
I initially installed a cast aluminum replaceable-element primary filter in the spare tire well like Woody6, and plumbed the return line into it along with the fuel feed from the crossover pipe; then I also had the pump and high pressure pump in there. One thing is that if you have any leakage at all then the trunk will smell like fuel all the time.
I ended up going away from that setup and now have the primary filter, pump, and high pressure filter all mounted on a piece of 1/8 aluminum under the trunk, just behind the spare tire well. The return line tees in just ahead of the pump. Going forward, the return line ends up following pretty much where the original feed line went. The feed line runs more outboard, and it ends up going through the right front fender well to come out to the engine compartment about level with the front of the right cylinder head. Then the fuel line runs rearward past the carburetor inlets, and then to the pressure regulator mounted on the firewall, where it plumbs into the return line.