These tanks are for sulphuric acid, and about 13.6K gallons. The MDC tank is a ~20K gallon tank. The proportions are a bit similar since the acid tank bodies are pretty narrow, but it's scaled up by a percentage factor, being both longer and fatter than the smaller acid cars. These 20K cars were often used for corrosives like hydrochloric acid, but sulphuric acid is heavier and shipped in smaller cars.
mu26aeh mentioned Athearn in HO and is correct - they did do the Union Tank Car version in HO scale. The prototype photos at the head of this thread showed cars from three different apparent builders, including one UTC version.