how bout spending 350 for some nice allpro 3" springs?
http://www.allprooffroad.com/9504tacomarearsuspension/9504leafspringsI had some 5" in my old tacoma and they were great
EDIT: I didnt tow with them but they were nice and arched even with a huge load (till i modified them and pulled two leafs out for more flex) but at least youd get rid of the block