I have a W and G level meter SPM12.

If you could tell me the IF o/put freq of this or similar units I could
make a bfo for cw/ssb o/put.

Not sure if this applies also to the SPM12, but I have used temporarily
a Selective Voltmeter from W&G which had a last IF output at 10 kHz.
You need a product detector, implemented either in hardware or software
(at this frequency it is practical to do it) for SSB reception.
Unless I am mistaken, the latest version of SpecLab from Wolf  DL4YHF
has an I/Q demodulator that could be used for this.

73  Alberto  I2PHD