Carb not getting fuel?

[White70C20]

Today I was able to work on my '71. As I wrote in a previous thread, my friend gave me the truck saying that the last time he started it, it had a knock to it. He thought it was a spun rod bearing. He immediately shut it off and left it sit for 2 years. I just got the truck on Friday, and almost got it started today. I want to get it started so I can determine the source of the knock. Some of you guys think it could be the fuel pump or a stuck lifter.

Anyway, as recommended, today I changed the oil and filter and replaced the fuel filter as well. Since I am planning on rebuilding the engine this fall, I put one of those clear inline fuel filters on so I could see if I was getting fuel to the carb. The fuel pump must be working somewhat because it filled the filter, but it isn't getting into the carb. I tried cranking it several times, but it won't start.
I looked into the carb and moved the throttle. I couldn't see any fuel squirting in, and for as much as I had moved the throttle it should've smelled like fuel, but it didn't.
Is the fuel inlet clogged? Besides removing the carb and rebuilding it, I'm not sure what all else I can do.