Sorry, I didn't quite understand your answer to my first question. If I do a clean install on the SSD it will now become the C: drive?
Drive letter designation happens on first available basis and it's determined by the drives that are installed and partitioned with a MS filesystem (fat or ntfs)
With nothing holding a drive letter, then the SSD should take C: Of coarse there's always these gotchas like card readers that may take C: too...
When I reconnect the HDD it will become D or F or whatever, but will not boot, but be recognized with all data intact?
In theory... It may also remain a C: at which point you would need to change the drive letter. In any case, the data should be intact.
The goal was to just be able to pick, move and delete programs and files off the old HHD at my leisure rather than back up everything and restore as is.
What difference does it make if you're using the new to copy from the old, or the old to copy to the new? They both read NTFS.