My 70 Malibu build

[Quadracer392]

I got three boxes of parts today. The firewall insulation pad came along with the fat mat, new valve springs, double roller timing set and heater box gaskets... I went ahead and put some of the fat mat and firewall insulation pad on so I could mount the heater box back up and get it out of the way. Since I put gaskets on the outside heater box to firewall, do I still need to put some sort of sealant around the box? I thought I read somewhere that you needed to even with the new gaskets?