Hmm, sounds like I'm in over my head on converting/building a guitar amp to run on both SV83 or EL84. I didn't follow anything in that last line.
I've built a half dozen kits, cobbled a couple guitar amps from scratch, and serviced several dozen Fender amps...but all of them I had a layout to follow...it was just like paint by numbers to me. I just copied what I saw in front of me with no understanding besides basic safety. Every amp I've built and serviced fired up the first time, but that doesn't mean I learned anything.

If I have a two EL84 amp I wanted to change over to SV83, is that possible or would I require all new output transformers? If I had an example to follow, I could easily wire the pins to what was needed, but as I said, I'm not sure I follow you.