Bruce for this weekend I think you need....... VP N20. It's got a high SG, real slow distillation curve... perfect for an n/a combo. :-D
Seriously, if you're no higher than 16ish to 1 in compression C25 is your best bet... but it's pricey... Very aggressive dist. curve, low octane for a fast burn makes good power. But it's NOT forgiving. If you're on the edge in terms of compression(near 17+) you need to be right on the tuneup when the wind changes direction or you'll nip plugs and smoke pistons.... C14+ runs real close to 25, half the price. If you're detonating a little more than you like with 25 then 14+ might calm that down some... the distillation curve is a little slower, still has a good low SG, and a little more octane. IF you're over 17:1 then I'd run something like C19.... C19 is a great fuel for a detonation prone n/a engine. The stuff makes good power. Still has a low SG, and the distillation curve is actually a slight more aggressive than 14+.... but with a point more octane.... C21 is an awesome fuel for high compression n/a but they stopped producing it.
That's all based on my own experiences. Of course cranking compression comes into play here too... with a host of other design parameters of the engine... but above is a general outline.