Thanks for all the replies.
It's not a question of making a GMRS antenna out of a CB antenna FOR MY APPLICATION. Yes, I could easily purchase a proper antenna. The reason I'm even asking this question is because I have a WWII Jeep with an antenna that would be originally used with a BC1000 pack radio that TX 40 - 45 MHz. The antenna is 10'8" long. I'd like to use the Baofeng hidden inside a radio case that I purchased that has it's guts removed (someone else, not me). Ergo, the radio would appear to work but using a GMRS radio inside.
Thanks,
Dave