@forbigger, I take it you've read the many tube-related posts in the BHSE thread? If not, you really should. Quite a few at the beginning by Elphas, then loads in the last year. It's not easy to distill all that information (including EL34PH reliability issues) into one post.
In a more general sense, any old or new EL34 or 6CA7 should be fine, and you probably won't need to adjust balance/offset - but I personally would want to have a dvm around to check anyway.
I don't know much about KT77s, but they are further from the EL34/6CA7 spec and so I'd keep the KT77s away from the BHSE. After all, there's hundreds of EL34/6CA7 models around, so you already have plenty of choice. And because there's hundreds of them, there's no point in compiling a compatibility list. What is more worthwhile is to produce a list based on Sound Quality, which Elphas, Golfnutz and TheAttorney (and others to varying levels) have already done in the BHSE thread.
I understood that the stock Mullards supplied by Justin were JJs. A number of headfiers, including me, have stated that these can easily be beaten on SQ.
And Justin has also provided the Shuguang Treasures as an optional extra.