440 Header/Head Mounting Bolt

What is the thread length and pitch for the header exhaust bolts going in to the heads (#906)

I have a tiny coolant leak I want to try to fix, only near the #6 plug

I think the PO might have used too short of a bolt for mounting the header

I took the bolt out and wrapped it with Teflon tape......still dribbles

Should I drain the coolant past the head and apply a thread sealant to or RTV to the bolt ?