This will depend on a couple things. First are you planing to try to use the existing output transformers?

A push pull, pair of 6V6 is usually used with transformer input impedance of about 10K or so. With parallel
6v6’s it is probably 5k or so.

Another thing this is actually two amps and this is low end so how this transformer will work full range is an open question.

Let’s start with that…John