Re: MSD Return line kit
I installed my Atomic EFI just about a year ago. At first I was running it returnless but had some heat vapor lock issues. I ultimately went to a return system with a regulator but I used the existing steel fuel line as the return. I also installed some hose heat insulation on both the feed and return hoses from the TBI down about 40" to just past the firewall in an effort to keep the engine heat out of the fuel lines.
As for your vacuum question, NO! The fitting on the regulator is a vent only. You must run the vacuum advance canister to a ported vacuum source on the throttle body. Your installation instructions will clearly indicate which connections on the throttle body are ported and which are live vacuum.
Speed has never killed anyone. Suddenly becoming stationary, that's what gets you! Jeremy Clarkson