Nice postal card.
Of course, as to the Model T's engine and transmission overhaul price offered by the sender, Wiki suggests that the 1920's Model T's were selling for $290, so $25 to overhaul (plus parts) would come up to roughly 8.6% of the car price (plus parts).
In 2011, if we had an old car that we purchased for $25,000 and were told an engine and transmission overhaul would cost us 8.6% of the car price, that would be $2,150.
Some interesting history on the postal card at this site:
http://blog.hemmings.com/index.php/...orth-dakota/Philatelically speaking, what I find most interesting is the addressee's location of Maxbass, ND. Although in 1930, the population of that "city" was 217, as of 2011 the population had dwindled to only 84, yet according to USPS.COM it still has an active US Post Office!

Yet according to this February 2011 article, it may be on the chopping block:
http://www.minotdailynews.com/page/...concern.html