So...why didn't the OEM spring seats get re-used?
re: 'Should that be on my new springs?'
Yes. Absolutely. Maybe they used new ones...but if you're looking at the old ones, I doubt they used any at all.
IMO..ask them. Sorry to be cynical, but I'd NOT ask them, 'Did you use new spring seats?'. They would likely just say, 'Sure!'. Show them the old ones..ask, 'What are these?' If they did the job correctly, they will answer, 'Those are your old spring seats. We put in new ones because the clips sometimes fail when they are re-crimped to a new set of springs. You gotta have those installed, but it's better not to re-use the old ones!'
If they say, 'Huh? I dunno.', take your work someplace else..they are losers.
If they say, 'Oh..you don't need those!', take your work someplace else..they are losers.
Yep. Hold the cap, turn the tube.
Racetech's have a larger diameter? Hhhmmm...I'd bet against that.
Cutting the stock spacer from 3" to 2 1/2" won't give you 10mm preload...not if your springs are even close to OEM length (470mm or so).
Based on that alone (if your spring length is 470mm and you specified 10mm preload)...you guessed it!! Take your work someplace else...they are losers.
Good luck!
Re: I am not going to be satisfied if it doesn't make the noise...
Sounds like you're all set!! ;)