Re: What caliber do you guy\'s recomend???
The Dakota's are Jeffery cases trimmed to about 2.5" for a COL of ~3.34", and have a bit more power than the Win Mag. The Excaliber and Pegasus, I think it is, are made on basically improved Rigby dimensions, or beltless Whetherby cases, you might say.
I do believe they are kept to OL of 3.6", but might be ~3.75". Either way, they're screamers, but for the money I'd do it on a Ribgy case if going long mag, and Lapua if staying within 3.6" COL.
With that large a case, I'd get at least a 28" bbl, and seriously consider much longer.
As for the Lapua AI, it doesn't look to me like you can even really get your money's worth in the straight Lapua Mag with less than 28" bbl, so there's no use in making more muzzle blast. In fact, with 26" tube, I'd take a RUM/404 case unless shooting heavier than 250g regularly. (Or 210 for .308".)