Based on the info given, the answer is It Depends.
You don't give enough information for anyone to give you an adequate evaluation. Conformation problems are structural problems, having to do with the way the horse is built/put together. Saying "no confromational problem in his life" doesn't really tell us anything. Every horse has conformational strengths and weaknesses; certain ones like verona mentioned, and others like long, weak pasterns or a long back will affect a horse's ability to carry weight.
There's also a big difference between a 180 pound skilled, balanced rider and a 180 awkward beginner. Also, a horse that can comfortably pack a heavy rider light trail riding might struggle doing speed events or jumping.
What I will say is that a 14.3 horse and 180 pound rider doesn't send up any red flags or alarm bells just on those facts alone. Now, if you told me the 14.3 horse has navicular symptoms or has been lame previously, the rider is a beginner trying to learn to run barrels or jump, wow, now I'm concerned.