I don't own an SLP-05 but would love to.
I understand that the N7s on the extreme right when facing the pre are for the headphone amp. I would roll tubes to my hearts content. I have tons of N7s and use good "cans". I might use that section to characterize some of the tubes I had. (If I tried that it would be a quite a long while)
If you don't have headphones or even care about that circuit then use "place holder" 6SN7s, perhaps the stock tubes, which are likely the Sino brand and aren't very good. Or if possible leave them out altogether.
The NOS/OS tubes you have are highly desirable. As such I might move the pairs around to find the best order for them. I would inlude the Ken Rad in a gain stage, if quiet enough ,for added bass energy or in a driver stage. If you are afraid of that, then call Dennis Had, to ask what he would do.
If you know what each pair is good at, knowing the sonics of the tubes you have, then you can make, at least, semi-intelligent choices.
Good Luck,
Sounds like fun.