Re: Best Mach Z
Too make a long story short, they will all be about the same... I would base it off of the cost of the sled you're looking at--Depends what you wanna Doo with it... The '96 has the C-7 suspension which is excellent for weight transfer = drag racing, but the engine is the older one, the 779. The '97 and '98 have the newer the SC-10 suspension and I think they both have the larger/newer 799 engine.
If you plan to trail ride it more, go with the CK-III chassis, if you plan on drag racing it more, go with the older F-2000 chassis... though the newer 799 engine has at least 5 more HP, they are close to the same speed because of the taller suspensions/ride heights (air drag increases dramatically because of the larger frontal areas--esp at 100 mph).
As far as modding them goes, there isn't much difference in final outputs--that's why I would go with the older one for racing (mainly cuz it will be cheaper to buy).
That's my opinion... hope it helps, even a little bit.