The cover band I'm in has done a couple songs that require slap, and believe it or not... my 73 Triumph does it most excellently. I'm not much of slap player, but can do it when I need to.
I typically rotate between the Triumph, 76 Thunderbird, and a 73 Ric as gig basses (one bass per gig). They actually all sound nice doing slap... round wounds and a compressor help. The bird and ric give off more of a 70s slap vibe (ala Mary Jane, etc..), but the Triumph can be more hi-fi/modern-sounding.