[68 TT]

6-1/2 psi is pushing your luck with an 1850 Holley. It may work fine or it may push fuel past the needle & seat. I have had some do that at only 6 psi and others be fine over 7. Just luck of the draw I guess.

I would lower it a touch just to be safe. Nothing worse than having it flooded at a stop light. As long as it can keep up with the fuel demand of the engine the lower pressure will be OK.

A vacuum referenced regulator that boosts pressure with engine demand is the best way to deal with it rather than hope the lower pressure can keep up.

Trick flow makes a nice one that is return style to keep your fuel pump working efficiently and it comes with adjustment springs to use it with a carburetor or with EFI.

http://www.summitracing.com/parts/TFS-27001/