Power Transformer For Marshall 18 Watt

[merlin]

Yes, I measured 172 volts and it has an output at 6.3 volts and another at 8 Volts

That sounds to me like you measured it unloaded. So it's probably a 160V, 5V, and 6.3V transformer under load.

If you have something like an 80V transformer you could add the voltages together, giving you 160+80 = 240V effective.
But maybe then the project is growing like Topsy.