Rushton may I be honored to say friend, There is a peculiar phenomena when it comes to the supply of old tubes. They come out of every nook and cranny when the demand goes up.
That doesn't address the issue of a low impedance speaker with an OTL sans autoformer. I have heard high powered ones with Avalons on a couple of occasions with excellent results. I have heard Ralph's reputed personal favorite the 60s with the undeniably true Frieds do a great job with the resistive load of the Real thing but have also heard tell of the 30s failing to power a demanding load due a less "benign" impedance load.
Thus get the power and/or make sure your impedance is very firm or will tend to rise before it drops.
That doesn't address the issue of a low impedance speaker with an OTL sans autoformer. I have heard high powered ones with Avalons on a couple of occasions with excellent results. I have heard Ralph's reputed personal favorite the 60s with the undeniably true Frieds do a great job with the resistive load of the Real thing but have also heard tell of the 30s failing to power a demanding load due a less "benign" impedance load.
Thus get the power and/or make sure your impedance is very firm or will tend to rise before it drops.