I have TRS drive cylinders. part# 87412A3 with the external lines. I wanted to know if anybody has any for sale? Also whats the difference between the ones with internal lines and external lines? Can you replace the external line cylinders with the internal line cylinders for a direct swap?
Thanks

Yes you can swap them. There are two lengths of internal line cylinders. The external line cylinders was a model upgrade that took place many years ago. The internal line cylinders would tend to leak from corrosion the newer doesn't appear to have that problem.
Jim