Carb jetting

[1970Custom]

So, I'm to the point of jetting down the Holley on my 300-6, I know what I need to get from/to (650-400CFM) only issue is where can I find out what jets I need to drop the fuel flow?

Thanks

 

[TexasNomad]

I"m not sure how low the jetting numbers go, my 302 with a 650 is jetted at #49, your going to have to try a few different sized jets at first also you will need to play with the float level maybe the power valve and squirter..
good rule of thumb with Holley's is when your changing your jets you want to find the jets that give you the best vac numbers with out going rich/lean..