Thanks RustyBucket, I appreciate the comments. I will agree about the 4 eyes thing!
I have not changed out the rear gear yet, although I sure want to. Mine too cruises about 70 MPH, overdrive, and 1650 RPM. Its very easy to run 80 or 85 before you realize it. I would like the RPM's to be about 1900 or so at 70 in overdrive.
I am running stock shift linkages with a modified tilt column from a van. And yes I can hold it in low gear manually. It took a few adjustments at the adjusting nut on the end of the column. I did add the 4 speed indicator to the column. The indicator does not exactly match the gear that is selected, but I can manually shift into all of the gears. Maybe try adjusting your linkage.
Be sure and let me know how the shock flip turned out.