I've been running a Holley 1945 on my 75 Duster for a few years without issues, always started right up even in the cold or when it had sat for a while. However, its suddenly started to surge when cruising, bog when accelerating and even idle poorly intermittently. I'm new to classic cars and I've tried to do my research but I'm still kind of lost on what could be causing the problem. Rebuild? Replace? Any help/advice I'd really appreciate. Thanks guys.

Have the fuel lines ever been replaced? Modern formulation of gasloines will melt old ruber fuel lines and clog the fuel filter and passages in the carb. All rubber in the fuel lines must be replaced with fuel injection hose rated for modern gasoline formulations. It must have "30R9" printed on the side of the hose.

I recommend cleanning out the carb and replacing any rubber hose in the fuel line.