Be honest in your descriptions, have multiple good photos and even photos showing issues/damage such as a dented boiler. Treat the potential buyer like you would want to be treated yourself. Don't surprise a buyer.
This past winter I sold a gorgeous DR Mercer traction engine which got destroyed in transit...despite double boxing etc., something VERY heavy was dropped on top and ruined the engine. Fortunately I had insured through UPS and though it took many months to resolve, I ultimately got a full refund and turned it over to the buyer...again, that is how I would want to be treated if I were in their shoes.
For highly valuable engines...I won't sell outside the USA as carriers won't honor insurance in cases of damage outside the USA, otherwise I will sell into most markets including Canada, Aust, NZ and Europe. Sorry to say I just don't trust shipments to Latin America.