Yessir, regular long scale work fine. The added distance to the tailpiece makes up the difference. I use TI Jazz Flats (made for 34 scale) on mine.
I was counting up, and as long as I've been watching these, I have seen maybe five or six of these Spoiler and Persuader 5-string models for sale, one if them (the one Dan ended up with) twice. There's just a dozen or so in the whole Showcase section. I think the whole 5-string bass was just starting to catch on in the 1980's. Maybe Mica can shed some light on when and how that took off with the Spoiler/Persuader and Distillate platforms, or roughly how many there might be?
I'm 100% sure there's a thread here somewhere that our own Jimmy Johnson commented on using a Spoiler 5-string (or maybe it was a Persuader) to finish a tour after his #76AC418 was infamously stolen. Can't remember where it was... anyway, I've often wondered if that was his preference to the cone headstock began.