My car stalls when I put it in gear. But thats not all.

I inherited a 1976 Mercedes 280 S from my dad and it hasn't driven in 1 year until recently. He said they did some work on the carburetor, The car has a little trouble starting. But when it finally starts you need to keep your foot on the gas or the car will stall. When it is at normal idling temperature it doesn't stall but if I put it in gear it stalls. If you you get the car to move then it doesn't stall at all. Then you can put it in gear and it still idles with ease. But if you drive it it feels like it isn't getting power because it the revs climb very very slowly even in park or neutral.