Help needed on painting 340 callout stripe on 1/18th 69 Cuda

I got a 1/18 diecast 69 Barracuda fastback about 20 years ago. My 69 Barracuda fastback is F8 dark metallic green with a white 340 callout stripe. I do have a little paint left from when I painted my car, so I completely blew the model apart to paint it. The model currently is a dark green with a 383 callout stripe on it. I want to paint the model with the left over F8 green paint and add the 340 callout stripe. I am not a model expert, so if anybody has any ideas, I am all ears.
My idea would be don't

When I was heavy into modeling j found out you could buy waterslide paper in clear and white, both in laser and ink jet capatability

I would use ms paint to make my decal and scale it down
Then print it on the waterslide paper and done

I think I may still have a model I did that too around somewhere, ill post some pics shortly


So in this case, I would Google a decal sheet from a 1/25 car, rescale it and done