Firestone manufactures an awesome AG style thread tire in 13.6x16.
Go to; http://groups.yahoo.com/group/ihcubloboyseries/
In the photo's there are the firestone ag tires your looking for.
So far i have found out the firestone tires are the best on my cub cadet's. I haven't tried the goodyears yet. But my firestone turf and field tires haven't shown any wear yet in over two years now over the cheaper turf tires. There's an old saying we get what we pay for i guess. I did purchase many pairs of the cheaper turf tires too.
The only other option for rear turf tires on the int154 number series tractor is to use the fcub rim centers and use the fcub rims with AG tires. I was thinking of doing this with the 9,5x24 or the 10,2x24 AG tires. Its nice to have other options.
My last of three 154's came with the 8.3x24 AG goodyear tires. You can get two imported 8.3x24 ag tires with new tubes on ebay too. Another option.