GM didn't deadhead TBI and TPI because there is no way to get air out except through the injectors. I suppose you *could* do that if you really wanted to, but even then the FiTech 40004 may not be the right thing anyway. It's FPR is factory set to 58 PSI. I believe the Holley tuner allows you to set the fuel pressure, so you could probably work with that. Your HSR has it's own FPR on the downstream return side of the fuel rail. It's factory set to ~43 PSI. If you use the FiTech and deadhead it, the injectors will see 58 not 43, hence tune it to 58. Being able to use a pressure as high as 58 depends on if the HSR injectors can perform OK at idle as the duty cycle approaches 0.
If you decide to add a return then the FiTech FPR is basically useless since the HSR will regulate to 43 (as long as the FiTech puts out something greater than that - and it will - 58 PSI). According to the HSR install guide it's FPR can be adjusted if needed. It also has a feature to connect manifold vacuum to it's FPR, making it a vacuum referenced FPR or VRFPR, and from what I understand Holley tuner s/w allows you to configure fuel pressure baseline as well as VRFPR settings. That is a nice feature when you have a 450+ HP engine to get more dynamic range from the injectors. The VRFPR will put out low pressure at high vac (idle) and high pressure at low vac (WOT) allowing the ECU to expand fuel delivery range of the injectors. It can provide a small amount for idle and a lot for WOT. It's highly unlikely that the 383 will be producing power that makes that feature useful, but who knows. It's there if you want it and would not be there if you deadhead it - unless the FiTech has a vacuum port for VRFPR (I didn't see one if it does).
IMO the surge tank that was linked a few posts back is a better choice because my personal preference is to run a return and have it plumbed back to the surge tank, not to the return to main tank like in your drawing, which is the only option with the FiTech 40004 deadhead design. That way the low pressure system has it's own closed loop supply/return to the main tank, and the high pressure pump has it's own closed loop system to the throttle body, with the surge tank joining the two. If I already had the FiTech I would probably use it rather than throw $300 at another surge tank. But if I didn't, I'd go with something else. The powersurge or whatever it's called is simpler, has better supply/return routing, less internal stuff (FPR) to misbehave or get in the way of the HSR tuning, and cheaper.
First and foremost with EFI is having a good stable fuel pressure - a good pump and good solid wiring to the pump - tuning depends on it more than anything else. Incidentally along that line, when selecting a pump, bigger is not necessarily better. You want enough flow to meet the HP demands and not too much more, because a overly high flow rate at idle can overwhelm the return and cause the pressure at injectors to rise over the regulator set point. That can cause grief with the tune.
Just my 2 cents.
