What can I fill holes in my firewall with?

[MoparGuy]

I've just installed air conditioning in my Charger & my new air cond lines are smaller than the original holes for the heater hoses.  As you can see in the pic there's a gap I need to fill around my air cond lines.   Is there a plyable material that I can mold where I need that hardens & is preferably black in colour?  Any specific suggestions with names of material would be appreciated.  In advance thanks for any help.
Enjoy the Chargers this season.
MoparGuy

[tan top]

could use a couple of rubber  grommets , 

[Fitz73Chrgr]

Bubble gum

[mikepmcs]

Yup, I agree, use some rubber grommets.  They would fill those holes up nicely and have a neat appearance as well IMO. Looks like one is needed for the far left black hose as well.(the one you don't have the red lines pointing to)

[plum500]

Couple of generic Mr Gasket valve cover grommets may fit - or maybe a couple of modified body plugs..

[PA Dodger]

Eastwood Resto Products carries this stuff. Not very pretty but sounds like what you specified.

http://www.eastwoodco.com/jump.jsp?itemID=1621&itemType=PRODUCT