Bagged 1969 C10 (new here & looking 4 help)

[scrubthug]

What's up guys?? New C10 owner here.. 23 year old from Myrtle Beach, South Carolina.

Coming to look at all of your cool trucks, but to also get some help. I normally mess with fords (own a 67 f100 & mustang).. so I'm having to teach myself the tricks and turns of Chevy stuff.

1969 C10 with a cammed 350 that has been bored over .40 backed with a 4 speed manual gearbox. This thing sounds mean. Love it!! But I have one small problem. Only happens when I try to keep a steady speed. It's like the truck is doing a chugging movement.. will move your whole body back and forth. In 4th (overdrive) it doesn't do it as bad, but has a slight chug and a very quite backfire/misfire sound. It idles great, when you give it the gas there is no hesitation.

Could this be a carb problem? Maybe the timing needs to be adjusted? I'm not sure. Any help would be much appreciated or if you guys could point me in a direction of forums I need to check out. Thanks for your time and I'm happy to be a part of the C10 Family!!