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From what people have said on the forum, if you rebuild just the top end and the motor is tired, then the bottom end will go out soon after because the fresh top end holds more pressure and produces more power than the original top end the has worn out the same as the bottom. So, if your rebuilding the top end, I'd refurb the bottom end so it holds up. As far as the kit, ive never looked into them so I dont know what kind of results it would produce. Good luck with the build!