Car is going to be painted on the bottom and inside with Rhino lining. Not sure if that is a geographical term or not. If so, it's the stuff people paint the inside of their truck beds with. Should never allow rust and will dampen any vibration or sound. Shouldn't have to worry about touching up the underneath paint then. What headers did you use? FPA makes a set of shorties that fit the 514 and allow for running exhaust pipes without hitting the x brace. Will probably suffer a little on higher rpm's though in comparison to a hardtop with tri-y headers.

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64 Galaxie 500 XL (constantly morphing)
FE 431 Stroker, C-6, Comp/Crane Roller assembly, FPA headers, Edelbrock heads, Zex n2o, Hydroboost.