In this first pic my question is does it matter how the rails are plumbed? Due to how I am going to have to route the fuel lines I was thinking about following the frame rail like factory and mounting the regulator on a bracket off the boss on the front of the cylinder head. And have the inlet to the rails start right behind the alternator and have the crossover line towards the firewall and plug the end by the A/C compressor.

In this second pic you can see how close the rail is to the A/C compressor I don't think anything but a plug in the rail here will work. There is only one inch clearance.

Here is the regulator I am using. The way I understand it if you are using a regulator before the rails this should work? First custom efi setup would like to not mess it up. Thanks

Yes that should work. Is there a return line that hooks to that regulator? On my Duster I'm putting the regulator in the back of the car by the fuel tank so the return line is super short. Then I just run the high pressure line up to the front and dead head the rails like you are planning to do.

You'll probably want to put your fuel pressure sensor at the end of the last rail up by the compressor. That way you'll know what the fuel pressure is at the end of the system.

On '70 I ran the fuel lines as original (mostly) and mounted the regulator on the right fender well. My system was originally a "loop" system. Pump to one rail, crossover, exit second rail and regulator. My regulator is vacuum referenced like yours and I run a return line.

On freshen, my engine builder convinced me I needed to feed both rails equally so the last injector does not get lower pressure. I now feed both rails through a fuel block, "T" the return and then to regulator. The fuel block is under the manifold and feeds the front of the rails with return on the rear. Still a "loop" system with better balance between rails.

I do like the loop style for bleeding the system... after service or after sitting. In a few seconds, all the air is out.

Yes it has a return its on the bottom on the regulator. Not sure about fuel pressure sensor? Do you mean a pressure gauge? the regulator has a port for one but I can't decide where to put it. The engine bay is tight I thought about putting it in the back like you are that might be my best bet. Should I drill and tap the end of the rail for a gauge? Thanks

There's "tight 90°" an/o-ring elbows out there for the end of that rail.

I have my regular on the back of the pass side rail, cross over in the front, and my pressure isolator for my interior gauge on the back of the driver's side rail. Never had any issues.

I did my efi conversion like a lot of newer vehicles with the regulator back by the tank. My first though was the fuel needs to flow through the whole system but so many modern vehicles do it so it can't work that bad.

I used the factory vapor line as the return but when/if I EFI my Coronet I'll likely do the same, no reason to run all the extra line and run the fuel back and forth

Here is my engine bay is setup from a year ago. Its the same now minus the wiper motor.

My first EFI system as well and has worked flawlessly on several track days, thousands of miles, and even in crawling traffic on hot days. I run Aeromotive but do not recommend their stuff since finding out a bunch of current products are Made in China.

I studied their diagrams and built my full return system off that. A benefit is that it keeps the fuel system cooler when road racing.
https://www.aeromotiveinc.com/fuel-cell-diagrams/
I run an ATL fuel cell with an internal 255 Walbro pump to a 10 micron then 100 micron filters. I use XRP stainless braid underneath the car along the factory fuel line path to a one way valve to my Y block. From there it splits to the two fuel rails. There is a bracket that supports the regulator. I run XRP Race Crimp stuff as its easy to measure and install, PTFE lined to use with all fuels.

I was told by Rich at Fastman EFI to not dead end fuel to either fuel rail, it needs to circulate back to the tank through both rails so one side of the motor doesn't see different fuel pressure than the other
I'm plumbing a hemi motor for dyno testing now and will rearrange the fuel system and wiring after this once the motor is in the car.
I'm routing the fuel feed from the pump through one side fuel rail and then looping it on the back side to the other side and then back through the regulator and then return it to the cell
Lots of fun joining this generation of fuel controls
Better now than later

Don't know anymore than my own experience but mine has run fine and with a eddy rpm perf intake I've managed to have 8 spark plugs that are virtually identical over 8 years of street driving.

Mine deadheads at the rail, the filter/regulator is back near the tank. Seems to work okay thus far, but I do get a few psi drop when i really nail the throttle [logged near the rail]. As long as it's consistent, that's all that really matters..

You want to minimize any "dead heading" if possible. With a dead headed fuel system an air bubble (from cavitation or a low fuel tank level) needs to flushed out through the injector which can cause a rough spot. Also, full flow plumbing keeps all the fuel at the same temperature. It's just a better way to go.

...works for every factory Hemi since 2003. (and many other OEMs)

Their pumps may be pwm to help with temperature, but that won't help the bubble problem.