For jumpy 1:10s, you cannot go wrong with GMade Aerations. They're completely underrated and not given enough praise. They have a 93mm shock which, if 3mm is too long, can easily be internally limited to meet your length requirements. They have 3.5mm shafts, and when built correctly with silicone grease, are butter smooth and do not leak. I used to run them exclusively on all my race LMTs and retro clods. Those trucks jumped better than anything on race day and made lots of people mad because they all ran overpriced Pro-Line Powerstrokes which are nearly impossible to get a good tune on.
GMade 93mm XD Aeration Shocks
They also come in a piggyback version which may look cool on a pre-runner:
GMade 93mm XD Piggyback Shocks