Anyway, there are some 'errors'
"CATALOG FROM DISK IN DRIVE :8" sould be 0 instead of DRIVE: 8 OR it should display like this: "CATALOG FROM DISK IN Drive: 0 UNIT: 8"
In C64 mode a LOAD"$",8 shows the directory of the "build in" disc. So I think that 8 is the correct drive number?
In -> Singledrive Units, ommitting the Drive parameter always uses DRIVE 0: and never refers to DRIVE 1: (which ist second DRIVE in DualDrive Units).
Siehe WIKI ->https://de.wikipedia.org/wiki/CBM-Diskettenlaufwerke
"
Commodore-8-Bit-Diskettenlaufwerkseinheiten („Units“) waren deshalb eigenständige Computer mit einem oder zwei vom eigentlichen Computer unabhängigen Prozessoren. Eine Unit verfügte über ein oder zwei Laufwerke („Drives“)."
Add: I can also imagine that on the C65 they use DRIVE:0 for the internal Drive and use DRIVE :1 for the additional Drive in the mini-DIN externaldrive connector (mostly not fitted). Because reading 'preliminary manual' they clearly state that the external drive is handled by the internal FDC circuitery..
Don't confuse with the IEC, because that one is for older drives (1541,71,81) and for CBM-printers.