ok, this is quite simple.
ecklers says they must be balanced using the lugs, NOT the center of the wheel.
https://www.ecklers.com/corvette/corvette-vintage-wheel-works-v45-17x9-2-piece-wheel-1968-1982-25-348169-1.html
This "should" be easy to confirm by simply calling vintage wheel works and asking their tech department at (714) 278-1600
If they do need to be balanced by the lugs, you can have the wheels mounted by the lugs then have them checked for balance. If they are just a little bit out of balance, look at the edge of the rim (not the tire) while the wheel is spinning and see if it is true or not. If the wheel is true, have the tires removed and spin up the wheels only. This will tell you for certain exactly how much the wheels are out of balance and how much the tires are out of balance. If the wheels are out of balance by very much or untrue, simply call VWW and tell them and see what they say.