Hi Mike,
Gates used the same output network for over half a century. A simple "T" net for harmonic suppression, as opposed to the usual ham PI net.
You can simply cut & try a bit at low RF levels so as not to have HV and burned fingers, a grid dip meter is a real help here.
The "T" cap may be shifted for better efficiency, a variable subbed in here will make things easier.
The good thing is all of them are larger than you need for 160/75, so conversion is mostly engineering work and not spending $
.
The coils can be multitapped for band change, as well as the driver LC net. 40 is doable, but the long leads make it really tough to stabilize.
If you muster up around 5W to bat the 813, a VFO input is easy as it eliminates one stage (the 807). If less drive is planned, the 807 is easily pressed into service as a gain/buffer.
Get yourself a real broadcast limiter with a hard balanced 600-Ohm output, not some consumer thing for PA use. Don't over EQ, your transmitter is HI-FI, so try and run it as open and natural as possible with a good mic like an RE-20 or even an SM-7.
Look to get some 95-98% negative peaks, with limiter polarity favoring the positive without too much asymmetry as it will just make things uncomfortable.
Have fun, put it on wheels, and you will enjoy it forever.
73DG