I've never seen an IAC packaged like that. What is the make and part# ? I had to chuckle when I saw your NOS Y-block getting the supply side fuel split into the fuel rails. I have a Fragola 900609BL splitter just like it that is -8 in and 2 x -6 out. My fuel rails are -6. I have concerns about a single -6 being able to feed 1000 HP running E-85. I chose the pricy Fragola Race-Rite PTFE hose because the -8 hose has a true 0.500" ID. Several other -8 PTFE hose brands have a 0.405" ID. That observation got me to measure all the IDs of my -8 and -10 hose ends and adapters which lead me down another rabbit hole. Then I read the Kinsler NASCAR EFI paper about heat soak and bubbles and flushing the bubbles with the key on fuel pump prime at startup. That made me think about putting the fuel rails back in series to guarantee a good vapor bubble flush prior to a heat soaked start. I also am considering mounting the regulator to the inner fenderwell. I wanted to mount to the engine for simplicity but reconsidered after reading Kinsler 's recommendations on where/how to mount the regulator. If I do mount to the engine, I'll soft mount the regulator to protect from vibration. And all fuel lines will get some type of insulation to try minimize heat soak. Then I started to wonder if I'm way overthinking this whole thing . But I'd prefer to spend the $ once and not have to re-spend to fix any design screw-ups. So when are you planning to do wasted spark or COP? Seeing a distributor on that EFI engine looks weird!