After spending most of the day trying different thicknesses of shims to get the most rigid, but sliding fit the carriage is back together. As I had hoped a 1/4 turn of the rear cap head screw locks the carriage.
I also cut a spacer/shim to fit on top of the feed nut to do away with the need for rocking about a grub screw. I have left the grub screw in place to stop the hole filling with swarf but it’s no longer functional.
This is the spacer in place before attaching the cross slide.
Next was reassembly of the apron, cross and compound slides ready for a test run. It all went back together nicely but getting the main lead screw cover in the right place for the power feed half nuts to engage/disengage properly was a right pain and took several adjustments before everything ran smoothly.
I still need to make a couple more spacers/shims to take more backlash from the cross slide but I needed the lathe back together to turn them.