I got a used holley 4150 carb form eBay it has been sitting for a long time what would be the best way to clean off the old fuel, rust, dirt and all the crap in this old pos

 

This is just my opinion and others will probably disagree. Stay away from the carb parts dip. Get some heavy duty detergent type kitchen degreaser (smart & final) and hot water. Use the degreaser full strength with various brushes and scrub the disassembled parts. Soak the small ones then brush with a stiff tooth brush. rinse with the hot (hot) water and blow it dry with compressed air. Then use aerosol can gumout to spray the small passages clean. Use "The Must For Rust"® for the rusty spots. Reassemble per instructions.