Wow, you have a major project going on. All the modifications youíre making sound great. Good luck.
Not sure what negative things youíve heard about the Goodyear Marthons, Iíve always thought them to be one of the best trailer tires on the market and Iíve always have had good luck with them. You could also consider a LT tire for your trailer.
When taking your trip, you may want to consider doing what many people do that take a trip to Alaska. Many recommend that you carry 2 spare tires for each, that is, 2 spares for you tow vehicle and 2 spares for your trailer. This gives you added protection in case of a second blow-out / flat happening before you can get the first one fixed. On one trip we had 2 blow-outs on the same day, 100 miles apart. DW suggested we get the first blow-out replaced before continuing. It turned out to be a very smart decision. My better half came through again. Iím learning never to doubt or question the wise advice of the DW