Andy gives solid advice.
I came to that same conclusion by myself and contacted him to check my sanity on it as well.
By the time you buy a set of 450R shocks, pay shipping to send them back and forth somewhere, and pay for the conversions, it just don't make great sense to me. If you picked up a set for next to nothing or are using the set you yanked from your R it makes a little more sense.
Same thing if you have a set of aftermarket shocks that need correcting. By the time you pay for Elka or whoever's parts, seals, etc, and pay for the conversion, piston mods or high flow pistons and so forth, and shipping two ways, it just starts to get expensive.
With the GT Suspension you get a shock built new for you custom, and already has all the mods you'd have to pay extra to have done, etc. The only down side I can find, and what makes them solid and reasonable, is lack of a lot of clicker adjustment. But if they are right to start with like they should be, it don't matter anyways and it's less stuff to screw you up. A lot of shocks, especially OEM's, have a lot of clicks that don't really do anything much anyways. Very little range.