Sandblast the frame, tape off and seal relivant areas. Have the frame powdercoated. I doubt there is rust in the oil tube, but a lot of crud. Rinse it out with a solvent prior to sandblasting. Also get a new set of studs, nuts and bottom plate for the oil tube, as you will want to leave the originals on while sandblasting and powder coating.
Plan B, hand sand rust, rattle can prime and paint.
The prep for sand blasting and powder coat is easy, but must be done right. If you decide to go that route I can help.
