The two files here were created with copytape.
I was able to create bootable tapes from them with copytape.
copytape sunos403-1 /dev/st0 worked on a Linux  box for this.

I found copytape at:
ftp://ftp.uu.net/usenet/comp.sources.unix/volume10/
and edited line 152 so perror didn't complain about too many arguments.

For the install, here are some abbreviated steps I used on a 3/80:

machine output		human input
>			b st()
boot st(0,0,0)
boot:			st(0,0,4)
from device:		st0
tape file number:	5
#			format
(proceed to partition disk, BSD style
label disk and quit format)

halt and reboot
		b st()
boot:		st(0,0,2)	copy program
from:		st(0,0,3)	miniroot on tape
to:		sd(,18,1)	copy to disk
boot:		sd(,18,1)vmunix	boot from miniroot
#		cd /dev
#		MAKEDEV st0	may already exist
#		MAKEDEV sd6	may already exist
#		newfs /dev/rsd6a
#		suninstall

At this point you're on your own.
