Flexcan Teensy help to complete project

I have a Teensy 4. with 3 can

Can1. VCM
Can2 Speed controller
Can3 Speedometer

Can 1 hard coded, it sends data using a lot of cob id that has to pass thru can3 unmodified.
The only id that needs to be modified is 0x18fef100 which corresponds to Speed and Parking brake light (byte0 and byte 2) The code needs to grab Byte0 and discard the rest

Can2, I'm using 0x481. to send the message data (speed) the code needs to grab byte 2 and discard the rest

Can3 Needs to write a message with everything in the BUS except 0x18fef100
Then Can3 has to write a message using 0x18fef100 using Byte0 from can1 and byte2 from can2.

Everything else in the Bus has to pass thru without modifications.






I have a code that is 95% working