[G6Tanuki]

One-side-of-the-heaters-grounded and using the chassis as return is just fine: RCA were quite happy to use it in the AR88!

And an auto-transformer to power the heaters is OK too - quite a few domestic receivers/record-players used the idea [some record-players used a tap on the motor's field-coils for this, reducing production-costs and parts-count, to the delight of 'product engineering' and shareholders alike]