Also, anyone have good suggestions how to fill in some component values and/or specific parts that would be a match?. The primary transformer seems to have a lot of additional windings on it so I'm guessing it may be difficult to get a single part when this one might be designed specifically for this application.

I've asked chatGPT to weigh in on this, here is the AI's response: Running 6SN7 triodes in parallel can provide several benefits in the gain stage of an audio amplifier: 1. Increased gain: By running two 6SN7 triodes in parallel, the overall gain of the circuit is increased, which can be useful in low-level signal amplification. 2. Lower output impedance: Running triodes in parallel can reduce the output impedance of the circuit, which can help to improve the amplifier's ability to drive low-impedance loads and improve bass response. 3. Lower noise: Parallel operation can reduce the amount of noise in the circuit, which can improve the signal-to-noise ratio of the amplifier. 4. Improved linearity: Parallel operation can improve the linearity of the amplifier by reducing distortion and increasing dynamic range. 5. Increased headroom: Running triodes in parallel can increase the headroom of the amplifier, allowing it to handle larger signals without distortion. However, there are also some potential drawbacks to running triodes in parallel, such as increased power consumption, higher heat output, and the need for careful matching of the tubes to ensure proper balance and minimize distortion. As with any design choice in audio amplification, the decision to run triodes in parallel should be carefully considered in the context of the specific amplifier design and the desired performance characteristics.