Hey Mr. Jeffery,
I noticed in the vision in Amos 7 that Amos had at two different times referred to God as the Lord (no caps and not as Jehovah). It also appears that Amos is visually seeing the Lord (no one has ever seen Jehovah fully), so could that have been Jesus holding the plumb line in the vision? I know Jesus is referred to as the Lord in the New Testament.
There are a number of terms that refer to God. In English translations, LORD (written in all caps) is the translation of yahweh. The word "lord" translates the Hebrew word 'adhon, which means lord, master or official. When it is capitalized "the Lord", it translates a similar Hebrew word 'adhonay. The word 'adhonay or 'adonai is used exclusively to refer to God. To prevent confusion, 'adhonay yahweh is translated as Lord GOD instead of Lord LORD that consistency would demand.
You can see them being treated as equivalent in: "The LORD changed His mind about this. "This too shall not be," said the Lord GOD. Thus He showed me, and behold, the Lord was standing by a vertical wall with a plumb line in His hand. The LORD said to me, "What do you see, Amos?" And I said, "A plumb line." Then the Lord said, "Behold I am about to put a plumb line in the midst of My people Israel. I will spare them no longer" (Amos 7:7-8).
A number of prophets have seen God in visions, such as Ezekiel and John, but this is not the same as actually seeing God. Thus, I don't think you can conclude that this passage in Amos is specifically referring to Jesus.