What a terrific opportunity for the Wendover Speedway Museum to both raise some cash and also publicize itself with wearable billboards. Everyone has an opinion, so here's mine.
Obviously, t-shirts have a front and a back display area. Use both.
The back should be the museum's advertisement. Have an illustration of the museum itself with "Wendover Speedway Museum" and "Wendover, Utah" above and below the artwork.
The front should feature a series of historic Bonneville land speed record vehicles (one per shirt), beginning with the Mormon Meteor of course, and progressing through the years. This will encourage collectors to accumulate the whole series over time. And spend more money. Contemporary vehicles can be left to the USFRA and SCTA, etc.
I also suggest going the quality route with sublimation printing. That process will result in a shirt that can be worn and washed without the degradation with a screen printed product. I don't believe a cheap shirt will result in more sales.
Can't wait to see, and purchase, the first ones.