Yes, you can try a new spring.
I don't have any New Models at the present, but as I remember, that as you open the loading gate, the cylinder latch should be pushed down, away from the cylinder to about even with the top of the frame (lower).
(Flatgate, can you confirm this?)
The new spring may be too long at the point where it contacts the loading gate....and that is where the fitting (shortening) may need to occur.
If you install the new spring, and then find that you cannot open the loading gate all the way, it's probably because the new spring is too long at that point.
I am also not sure about which spring might fit your New Vaquero. A quick call to Brownell's should be able to confirm which spring you need.