Idle steadily worsening

[dzbowtie]

Hey guys,
My truck has developed a rough idle over the last couple weeks. This started one day and went away but has progressively worsened.
To start with, I have a basic vortec headed 350 with Holley 600 carb. Nothing special, small cam, aluminum intake, daily driver.
I have always been able to pull the choke halfway or so, pumped once and the truck fire right up. Lately, I have been having trouble getting it to stay running once fired, until it warms up a bit. Then, it will idle between 700-900, surging up and down. I have never had this issue. It had idled steady around 800 in park.
When in gear, it usually idled right at 500. However, now when placed in gear, the rpms drop to 150-200 and almost dies out. When I tap the gas, there is a delay, then a surge where the fuel hits.
While driving home, the truck almost felt like it wasn't running on all cylinders. The rpms felt like they still wanted to surge. When I parked the truck, and since it was late at night, I felt for a cold header tube, but they were all hot.

My initial thinking is a carburetor issue. I sprayed some carb cleaner down the butterflies. I checked the vacuum lines and they all seem good. No cracks or open lines. I have put some carb cleaner in my fuel also, thinking maybe this will run through and help if there is an internal carb issue. I doesn't seem to have made a difference yet. My fuel cap was loose also, so maybe there could have been some water get into the tank from heavy rains, but again, this has never seemed to be an issue before.

My spark plugs and wires have not been changed in about 8 yrs but I haven't had an issue before. I have not had a chance to put a timing light on it yet. And I'm sure it couldn't hurt to replace them anyway.

Aside from this recent issue, the engine has always ran like a top. But this rough idle and surging is frustrating. I want to focus on the carb, but would take any help at this point.

I appreciate any suggestions