I'd go for an untapered 1:8 in either 24 or 26 inches. I've had 2 Contender barrels in the standard .223 in that format, and both shot everything from the stubby 40 grainers to the streamlined 75 grain A-Max with surgical accuracy.
The 75 grain A-Max really adds a good bit of thump to the round compared to the conventional 50-55 grain bullets. It is visibly more authoritative on coyotes, especially when you get past the 150-175 yard mark.
I could kick myself for ever getting rid of either of those, but I guess we all suffer from 20-20 hindsight now and then...