[DeTomaso] Air Conditionling flalr to O-ring adapter sealer?

[Ken Green]

I have an NOS Sanden 508 compressor with male flare fitting and am installing adapter fittings to use a hose with o-ring fittings.  The adapter fittings will be a permanent mod to the compressor and I want a zero chance of leaking with a small molecule refrigerant.  Any suggestions for a sealer between the adapters and the compressor?
 
Thanks,
 
ken