Duel gate shifter problems for 79 W-30

[Rcbreezy]

I seen this forum up before but it still really didnt help. the brand is hurst on the hers side its automatic and the right side im guessing its a 3spd shifter. 1st gear and 2nd gear im guessing runs ok but 3rd gear really does nothing abt make me roar the engine

 

[Rcbreezy]

Plus i have a edelbrock carb with 4 valves. should i get it rebuilt or jus buy a new one. lol i love my car but really need someone whogd at restoring cars