I understand that it is possible to convert the RL 450B to a 550B... To be precise, Dillon's website says to a "TL 550B".  What is the difference between the RL and TL 550B models?  Is there really a "TL" model or did someone just fumble finger it when they were typing in the web page?

Also, to do the complete conversion, what would it end up costing?  It seems from the web page, there are various parts that you need to replace, but I'm curious if there is just a single kit that does everything (hopefully for cheaper than the separate pieces, of course).