Aftermarket sending unit not the same

That longer one with few bends would bounce on the bottom of the tank, put more force on the seal, etc.. the design was improved so the aftermarket repops the improved one. You will find they both reach the bottom of the tank, even though not reaching out toward the center of the tank quite equal.

Both senders operate on a range of 73 ohms at empty and 10 ohms at full. You have stock or aftermarket fuel gauge ?