Which tubes to spend the most money on in a PV-5?

The information c-j gives is not enough for someone unfamiliar with the preamp to give recomendations about tubes. Call c-j and they will tell you what the purpose of the different tube positions are.

If I recall discussions here correctly, the input tubes have the largest effect on the sound, driver or output tubes less effect. Someone please correct me if I'm wrong.

I have a Rogue preamp and they replied to my email about which were the critical positions. Perhaps CJ would similarly help you. I think, however, that the signal position is the more critical, the driver secondary. It sure would be nice if CJ would help you with this.

I have a CJ PV10A which dates from 1992 vs 1984 for yours. Be wary of film capacitor aging. If your caps are solens/Axxon they are probably still ok. If you have other manufacturers, those caps may have degraded, collapsing your dynamics and transients. You may want to ask CJ that question if your pre hasn't been checked in a while. Do that before spending on NOS tubes. Replacing 1980's technology caps with wisely chosen current audiophile grade caps should rejuvenate your pre even with tubes you already use.