The bail bond money Jim was transporting was ten $1,000 bills. Denominations over $100 were no longer issued after 1969 and were not often found in circulation by 1974.
In the opening scene Rockford stops his car in front of The Great Blue Lake Land & Development Company sign. But this sign is parallel to the road, making it almost impossible to read while traveling on that road. Instead, such a sign would have been perpendicular to the road to allow travelers (and two sided as well for travelers traveling in either direction) to be able to easily read the sign. No one traveling on a road that sees the edge of a sign is going to stop in front of it in order to read it. This would be a poor marketing strategy to say the least! Therefore this sign would only be useful for the camera crew and subsequent television viewing audience.
During the final car chase, screeching tires can be heard as the cars were turning but the ground was all desert floor.
Rockford could have avoided the whole mess by simply keeping the bail money in his motel room and keeping his mouth shut (but which would have made a very boring episode).
Rockford never mentions to the sheriff that the man who stole his money was driving a red Triumph TR6. It's unclear if Rockford had the license plate number but his complaint should have at least included a description of the car.
The service station man tells Jim to bring his car back the next morning to have it fixed. But the next morning Jim is trying to pick up his money at 9AM (the time on the clock in Hart's office) and there would not have been enough time to have his car repaired. (Note: Rockford went to pick up his money before having his car fixed. Once he instructed Rocky to come to town with Harry, then he went to the service station to have his carburetor worked on).
Rockford's logic about Murry Johnson living in that house because he used a hidden spare key is flawed. If Murry Johnson did indeed live in that house, then surely he would have his own key and keep it on his person. Hiding a spare key outside would be in case the homeowner inadvertently locked themselves out, lost their key, or needed a neighbor to check on something while the owner was away. Hiding a key and using it on a regular basis is not something an owner would use on a regular basis. Not unless the owner wanted to become the victim of a burglary.