[folivier]

It would be both the placard and the tires. The coach has a capacity for each axle which is probably higher than the tires capacity. The advantage of the 365 tire upgrade is to be able to run lower pressure which would give a better ride. I think the weight capacity for 365's are higher as well. Once you're packed up and get weighed you can figure out if you need to move stuff around, then set your tire pressure accordingly.
Have fun!