Hey, I'd love to answer you question but I'm a little confused by your use of the word "competitive." Do you mean how much money would they be worth? How much money they could anticipate adding to the economy? Or something else?
You also might want to be a little more specific about what they would be producing. Conventional wisdom says they would be producing cotton, but many farmers in the years following the Civil War did not produce cotton due to the drastic reduction in cotton prices. Following the Civil War, cotton prices remained at extreme lows compared to the yield in, say 1810. Cotton remained the main crop of the South after the Civil War, but this did not mean it was a lucrative trade anymore. The explosion of the production of the cotton crop in the South in the leadup to the Civil War resulted in significant losses in parity in cotton yields (in real words, the price of cotton dropped catastrophically relative to its previous worth due to the massive increases in production resulting from the expansion into the old Southwest (that is, Alabama, Louisiana, and Mississippi) and the dramatic increase in individual worker output (efficiency). Although the demand for cotton increased exponentially, the production of cotton increased at an even higher rate, so cotton prices fell.
A good website to see worth of cotton prices and the change in demand/worth is linked here. There are academic sources to show where each data point came from.
Many farmers who owned their own land but were not wealthy enough to enter sharecropping contracts or other labor agreements were likely to farm some food - enough to get by - and some cotton - enough to make small amounts of pocket money that could be saved to purchase new tools, wagons, etc. 40 acres is a lot, and I don't exactly know how much a family would divide up that land based on cotton vs foodstuffs, and the worth of a mule depended greatly on its pedigree, but generally draft animals (particularly horses) were worth quite a bit in the Antebellum Era and retain an expensive price tag to this day.
If you'd like to learn more about the evolution of the commodity trade of horses, I recommend Race Horse Men by Katherine Mooney (obligatory aside that she is a personal friend of mine, but she is also respected in the field and is mentioned in a Pulitzer-prize winning book and has taught many well-respected historians as well). Race Horse Men mostly focuses on the value of prize horses, but it also does a good amount of detail on horses and other draft animals as well.
I may not be able to fully answer your question, depending on your responses to my questions, but I look forward to hearing back and doing some research!