If I were you I'd try and do some Tyranitar raids if you want another one. 125 is too much cost. But you have three of them (not counting that 37.5 level) you could power them up to the 32xx (33 level) range and they will be more than enough.
About that Larvitar - I would keep him for the future. Who knows - maybe TTar will get some other interesting options when it comes to new movesets.
Only double the candy cost to take a level 20 raid catch to level 30, and this has incredible IVs. I've yet to see a Tyranitar with IVs this good from a raid. And that is completely ignoring the stardust investment from 20 to 30.
If you want more Tyranitars for some reason, then evolving this one would be the better investment. Walk with Tyranitar or use rare candy if you need more candy.
If you do evolve, then you are probably hoping for Stone Edge since you already have so many with Crunch. Your have a Crunch powered about 30, if you were to power above 30 it should probably be Stone Edge, but your current Stone Edge has the weakest overall IVs. They might not actually be bad, but it is a psychological problem that you might be regretting later. shrugs
Once you reach max damage breakpoints, there's no real return for your dust investment, and even then 4 Level 30 T-tars will last longer and cause more damage than just 2 level 39 T-tars. It cost 75,000 dust and 66 candies to go lvl 20 to 30 (gaining 30 HP along the way), but 130,000 and 152 candies to go lvl 30 to lvl 39 (gaining 11 HP).
Taking a perfect to lvl 35 to max the Bite damage against Mewtwo might be worth it, but spreading it out will give you a better edge.
Bad advice in a TM world.
You could get WORSE moves in future, and be unable to change back to better bite/crunch/stone edge
Yet, if bite/crunch/stone edge are changed to better you can always raid for TM and change it for better.
Can't TM back to legacy moves. Waiting is NOT a good choice anymore