To your question I had the same.one and found those resistors on the rectifier diagram. I think its called the input transformer. look at both diagrams Original and Skunkie version

Can you only change the rectifier once you complete the basic mod?

I think he used two (2) 100R, 1W (101000JR500)

Good afternoon, I wanted to know what resistors you used here? Thanks

I have no technical knowledge of this but I have a 274b valve that came with the amplifier I was wondering if I would have to buy a 5ar4?