hey, i've got a few of these 425s as well, and was going to make something similar. scott dorsey said he thought that the built in transformer on the 360 module was a 1:5 triad, so i was thinking of maybe using the 1:6.45 oep for the input tranny. there's also an inexpensive edcor 8:1 that i was thinking about using in reverse, but i know it isn't shielded, and it may not have a faraday shield between the windings either. they're cheap enough i'll probably try both eventually.
the circuit on the opamplabs page is where i will start, but with the additional input transformer in there.