OP, I would ask Mr. Allen to confirm that there will be no damage to his transformers by running the KT150’s...and maybe have him put that in writing. While the amp may supply ’enough’ voltage for the KT150’s to work, as russ69 pointed out above, you will not get all the power that the tube can produce.
Personally, I would be more concerned about using a transformer that was not originally designed for this tube, but if the manufacturer is ok with that..so be it.