Here is the health bar trick so you can estimate the strongest
unit in the game to accurately use
Tachywaxon's tech trading tool.
First, open up your game options using the escape button and in the graphics tab select "Show Health Bars"
Zoom in as close as you can onto your strongest unit in your real game and take a screenshot.
Next, open a test game up and use worldbuilder to add units until your unit has about the same health bar as your real game unit.
Once the real game unit's health bar matches the test game unit's health bar when comparing screenshots, the strongest
unit in the real game has the same strength as the strongest
unit in your test game
If someone doesn't know how to take or access civ 4 screenshots, I can talk them through it in this thread.
Pro tip: If you have 500 screenshots, don't delete screenshot number 100 through 300.
If you do that and take more screenshots, Civ 4 will save them as Screenshot 100, Screenshot 101, Screenshots 102 etc in the middle of your screenshot folder and you will drive yourself insane wondering why the game doesn't seem to be putting new screenshots into your folder. You will have to take 200 screenshots before you start seeing 501, 502, etc.