I did my firewall hole behind the drivers side head..that way it wont interfere with hvac stuff...
Itll be a fairly large hole to get all the wiring and connectors thru...I used psi harness,,it comes with the grommet....you might contact one of the harness places...they may sell the grommets..
Heres a few ...
https://www.bp-automotive.com/produc...ewall-grommet/
https://www.speartech.com/product_p/grommet.htm