have not done it. See if gparted can do it, otherwise from commandline but you have to google it
If you convert that drive to GPT then it is a good idea to do so (you maybe can do with booting from the other drive but i am not sure). Shrink swap a bit or delete it. For ESP a 200-300 MB are enough. vfat, flags esp and boot. At the end of the day when you lsblk it has the type c12a7328… as the other one.
Maybe you do this after the conversion.
And then chroot and grub install and it will see it