seat belts for crew cab to fit car seats tight

[eke82]

i bought an 85 crewcab that the previous owner had taken the back seat out and had shelves for his business. i reinstalled the like new seat but the pick up had lap belts only in the back. i have young kids in car seats and i am trying to find seat belt that will retract and lock to hold car seat tight like my 99 yukon has. My question is does some one make an updated version or adapted seat belt out of the vehicles to make this possible?
thanks eric everingham