Looking at the Carvin site, the only 7-string neck I saw was a neck-thru with a paddle head. Didn't see any bolt-ons.
Now, Warmoth has done some 7-string options not listed on their site. I've seen 7-string Explorers and SGs complete with matching headstocks. Call and see if they could do a 7-string Soloist with Jackson pointy headstock.