The early 500 was better. CDI box had a better timing curve to it. Is what I was told where the only difference to the 98 version everyone else got. we are talking the dealer demo sleds. 97.5 finding one is pretty hard I dont know how many where made. I have seen a few around my area for sale that might be one. Hard to tell from pictures unless you see the build date on the sled. Black belly pan and moto cross handle bars with the zr 440 green pad is what to look for. Even the early build 98 600 EFI LE where really quick mine was. They had a cylinder up date done to them the ports where too big the pistons would tip and the rings would snag a port. I had the recall done should of never had it done the sled was never the same it ran good but no where near the power. Soon as the update was done I could tell. By just riding the thing it didnt have the zip. I sold the sled right after the update thats how disapointed I was in the deal. Rule of thumb on a cat is buy the first run sleds when they come out if you want a fast sled. The only fall back is usually they have germlins. I have always tried to get the first ones they ship out. My 97 440 was a rocket till they messed with the timing. I blew it up after they messed with the timing. With in 20 miles after I got it back. Then blew it up another 2 more times with in less then a 100 miles. I know I didnt get my motor back also the last time I got it back I did the repairs and the crank case was too clean looking. My 98 EFI LE would just kill all the other 600's around in its class till they up dated the thing. Look at the early f7 firecats how quick they where they detuned them also. If you can get a early demo of one them you'll have the quickest 700 on the planet. They really went. But again you had a basket case so pick your poison.