I bought one similar to this to use but haven’t installed it yet.
https://utmindustry.com/utm3502
A high performance, audio signal transformer for line level output applications. Gapped. Useful for 1176, rev A-E circuit.
Ratio: 1:1:1:FB
Impedance: 600Ω:600Ω:600Ω+feedback coli.
Frequency response @ 600Ω source, 600Ω load: +/- 0.5 dB 20 Hz to 80 kHz (Ap)
Primary Inductance: 500mH
Secondary Inductance: 500mH
Tertiary Inductance: 500mH
Total DC Resistance PRI: 35Ω
Total DC Resistance SEC: 35Ω
Total DC Resistance TER: 260Ω
Max Level: @50Hz: +32 dBu
Core Size: EI57, Z11 Oriented steel.