How steady should idle be?

[Dleslie212]

77 K10 with a Edelbrock 1405 carb, Edelbrock performer intake. As far as I know, heads are stock and I have no clue about cam. It has a 350 and a 700R4. It idles when in gear warm at about 700 RPM, but every ten seconds or so, it’ll drop about 100 RPM and then jump right back up. I also have an issue when driving - at about 3000 rpm, it will start surging down to 2500 and then back up to 3000, almost like I’m pumping the gas pedal. I have no idea if the two issues are related.

At first I thought it was a fuel delivery problem, but everything has been replaced now except for the carb, which still,looks almost brand new (no idea how old it is - it came with the truck)

My main question is about the idle - how steady should it be? Is it normal to have. A little drop in the rpm during idle, or should the needle on the tach stay pretty steady all the time?