For $400 you can do it yourself and a ton more if you're interested. If you do go the HPTuners route, I can give you the calibration changes needed for that tire size so your speedo will be dead on accurate.
If you're ever up in the SF Bay Area, I could do it for you. I wouldn't be free but it would be way less than $400. (The license fee for me to edit your ECM is $100, that goes straight to HPTuners.)
This is the hardware and software...
https://www.hptuners.com/mpvi2/#custom_form_mpvi2
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