Are you doing 50 watt or 100 watt? I've built a bunch of these (50 watters) and I've used a bunch of different iron: Ceriatone, Heyboer, Marstran, Merren, Mercury, Classic Tone. They all work. And they all sound good. I just prefer the specs of one or two over the others and some come with the PT wired with eyelets instead of hard-wired leads. I prefer the former since it makes for a cleaner install.
If you're going to build one yourself I recommend at the very least doing the following changes:
1. Add the missing 10K B+ dropping resistor between PI node and CF node.
2. Lower slope resistor from 47K to 33K.
3. Raise NFB resistor from 39K to 47K.
I know it's all personal preference but these amps sound much better to me with those changes. And if you're building the amp yourself you can just temporarily place in #1 and #3 to see how they sound in comparison to the stock values. But #1 is a MUST.