Under Hood Insulation

[swisschallenger]

Hello, I want to add the hood insulation to my 70 Challenger (H51) with an R/T hood. Which is the most correct version, as I have seen from Year One a molded type with a round cut out (for 70 model) and a variant without it, suggested for 71 model. What is the cut out good for? Thanks to the restoration experts for clarification.
Thomas