Any tack is acceptable, from treeless saddles and bitless bridles to treeded saddles and bitted bridles. Endurance is more laid back in the rules, as is LeTrec.
Any tack is 'good tack' as long as it is comfortable for horse and rider over long distances. Preferabley a light weight saddle would be best and one with lots of 'D' rings for saddle bags etc.
I believe Wally did endurance, she's be best to ask I think...