Don't know everything !

A friend of mine who owns two restored '68 Firebirds, a 350 HO and a 400, both four speeds, was told by a 20's something "knows everything" that his grandfather purchased new a 1964 Mercury Marauder 390, transmission type unknown, that was delivered to the dealer with a two barrel intake and carb on the engine with 3x2 carburetion in the trunk to be installed by the dealer. I've been around 60+ years and been involved in the automotive world for 50+ of those years. I know Chrysler very well and am not completely ignorant of the other manufacturers but my knowledge of their performance offerings is somewhat limited, I know in the '60's a lot of performance equipment arrived in the trunk and was dealer installed.

Was this 390 engine scenario a possibility with the '64 Marauder, I've been unable to find any info to this question on the net?

Thanks for your time and input.

My daughter slid into a brick wall last night, icy street, slow speed hit on left front corner of bumper cover, airbag did not deploy. Fortunately I have a nice bumper cover on an identical parts car. How long should I wait after disconnecting battery before I can safely remove damaged bumper cover without possibility of deploying airbag?