Can you mod the tti TCB-880 cb radio from 80 channel too 400 channel
1) Yes you can, any
radio can be modded. Some are far easier than others though.
We played around with a very similar one about 3 ago. Got it to do lots of strange things by adding random data to EEPROM IC802
OK so I was bored... it almost made it to 15 metres (after a VCO retune).
2) Why would you bother?
It's low end consumer grade (i.e. sold in auto accessory stores to people that have never used a radio before) junk.
If you want to go out of band, you'lll need a SSB radio at least, preferably a modded amateur "10 metre" rig, with an antenna and a power connection to suit.