Since I have 3 x Asus P5A rev 1.04 boards, I can confirm that not only Voodoo 3 cards work with this platform (and almost any other SS7 platform, except for those with AGP power delivery problems), but they are 100% stable in every possible scenario. I can leave 3DMark2000 running for 24 hours in a loop on these systems (with either a Voodoo 3 or a GeForce card) and there won't be a single glitch (a bit of tuning is required to achieve 100% stability with GeForce cards, though).
You can see this extended benchmark session I did on one of the P5A boards, with a modded & overclocked K6-3+, and a Voodoo 3 3000 OC @ 3500 clocks: https://www.youtube.com/watch?v=jFFNyexouGU
And the same platform with a GeForce 2 Ti @ Ultra clocks: https://www.youtube.com/watch?v=jrV6vPGR3Yc
If you are experiencing instability, then something else is going on (memory incompatibility, capacitor problems, semi-faulty video card, some other specific peripherals/PCI cards that you might be using, etc).
Capacitor problems are unlikely, though. At least all of my boards came with Rubycon caps from the factory, which are still in excellent shape (but not sure if this was the norm for all P5A boards or not).
2 x PLCC-68 / 4 x PGA132 / 5 x Skt 3 / 1 x Skt 4 / 9 x Skt 7 / 12 x SS7 / 1 x Skt 8 / 14 x Slot 1 / 6 x Slot A
5 x Skt 370 / 8 x Skt A / 2 x Skt 478 / 2 x Skt 754 / 3 x Skt 939 / 7 x LGA775 / 1 x LGA1155
Current PC: Ryzen 7 9800X3D
Backup: Ryzen 7 5800X3D