Can I put a car seat in extended cab truck with bucket seats IN SC?

This depends. Some car seats require 100% of the base of the car seat to be on the seat of the truck. Some car seats only require 80% of the base to remain on the seat. For example- the Evenflo Maestro and Graco Nautilus require 80% of the base to be on the seat in harnessed mode (Nautilus requires 100% base on seat for use in booster mode) so if the front-to-back length of the base is 14 inches (I'm making this up, I'm not sure what it actually is) then you may not have more than 2.8 inches hanging over the front of the truck seat. Some extended cab trucks have a portion of the seat that you can slide out to use for installing car seats- please read your owner's manual to see if this applies to your truck. I encourage you to read both the owner's manual of the truck and the instruction manual that came with the car seat, then try to install the car seat. Take pictures of your installation and post them on car-seat.org where certified car seat technicians will visually check your installation and answer any questions you have, or recommend a new car seat that may fit the child and the truck better.