I'm looking for a tank to replace the cracked tank on my mothers ZURN wallmount toilet, circa 1965. The tank mounts with two bolts, spaced 5 1/2" center to center (that's measured without disassembling)

Any tips, advice, leads on a replacement tank ????
I'm leary of replacing the wall mount that's been undisturbed for 45 years. Hoping (dreaming?) of a more simple tank replacement.

Thanks for your help and time,