hesitation, etc.

1965 Chevy C10, 292. I have a couple fairly basic question about hesitation, etc.
First, when I press on the gas suddenly when the engine is at an idle,
it nearly dies, then revs fine. I recently gave it a tune up and replaced the fuel filter, which gave it more power.
Second, when cruising down the street at a steady speed, it surges, if that makes sense. I can't think of a better way to describe it. It doesn't maintain a constant engine speed.
What things would normally cause these? I just bought the truck a couple months ago, and it is generally solid overall, but I don't know all the history. Thanks.
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