If you cannot get the gvp fassstprep floppy disk there are two other possible ways:
1) format the harddrive would be to use commodore's hdtoolbox in workbench 2.0 through 3.9
you have to use cli or other shell program navagate to hdtoolbox's location and type in:
hdtoolbox gvpscsi.device
double clicking on the hdtoolbox icon will default you to a scsi.device which is the default commodore scsi controller, ie a2091.
The problem with this method you really need workbench 2.0 or above..
2) connect the harddrive to another amiga with a commodore or gvp scsi controller. Then put it back in the a500-HD8+
I believe that the gvp A500-HD8+, the commodore a2091, and the A3000 scsi are all compatable. you can format a hard drive with any of these controllers and used it with any of the other controller, at least I have not had any problems.
This will not necessary work with other harddrive controllers like dataflyer, or IVS trumpcard.
lastly with OS 1.3 you can only use FFS (Fast File System) or OFS (Old File System).