Unfortunately I have not had any such luck to run any version of Solaris under the sparc64 emulation. It definitely works to run 32-bit Solaris 2.6, 7, 8, and 9 on the 32-bit sparc emulation however. If your application is 32-bit only (and only uses SPARCv8 or less instructions) then you can get this to work, but I don't think you'll be able to take the disk images from the Ultra 5. Much better to just install a fresh copy of Solaris and then copy over all the items you need (binaries, scripts, configurations, etc) to make your application work. I've only gotten it to work using old Sun firmware (linked below on artyom's page) not OpenBIOS, and only with 1 virtual CPU, and the max amount of memory using a SPARCstation-20 model is 512 MB, but this is enough for what I need.
There are some good guides for example - https://virtuallyfun.com/wordpress/2017/12/06/revisiting-a-solaris-on-qemu-install/ and artyom's page - http://tyom.blogspot.com/2009/12/solaris-under-qemu-how-to.html - also has a link to sun prom
