We have a classic, vintage motorhome.
We live in Michigan that does have similar, but not identical restrictions to Missouri.
We can legally drive it:
To shows and events,
For repair and testing (Mi has no distance limit),
The month of August.
It is not to be used as a daily driver.
We have had a year of manufacture plate for 14 years.
We are members of a type specific organization that has two annual conventions, and are invited to attend other chapters nationwide. Nobody said we had to take the short way to get there.
We have be stopped by local LEO in seven states twice because of incidences on the road (we broke something) and the others because the officers wanted to see her close up.
My sister and BIL have a similar coach and go all over with the authentic plates and have the same experience with interested LEO.
My advice: Get it, and don't sweat it.
Frank, 1973 GMC