I bought the shocks on ebay a few years ago for my Z400. They were still up for auction and I guess everyone forgot about them so I got 3 brand new shocks for $151.xx. I was pumped. But if the DS450 shocks are longer, then I should proably start with those, I think I read somehwere that the front shocks on the Rincon are about 18in front eye to eye. I'll measure them tomorrow while I have the tires off. Now did I read correctly in another one of your posts that you are swapping the DS450 springs with the ones from the 700's shock?The KYB DS450 xmx shocks are said to be better, but it's probably a brand name issue more than functionality. I have yet to see the TRX shocks go for less than $300 for the fronts alone. The word I have heard is that the TRX shocks are a bit shorter than the DS shocks. About an inch or so.
Find the length of the Rincon shocks eye to eye. That's your starting point.