I think they are both 40 gallon tanks. Should be markings stamped near the filler that will give info in lbs. and then figure 80% of that number. Be sure to check to make sure the certification date is current, of you won't be able to get them filled. Vertical tanks are required to have over fill protection valves later this year, but horizontal tanks are exempt at this time, but there is some confusion at the dealer level about this.
Denny