Personally I would skip right over 16" LRG tires and switch it to 17.5 rims and 215/75R17.5 LRH tires rated to 4805 pounds. G614's used near their max rating do not seem to do well. Sailun are maybe better however they are about an inch larger in diameter tan the G614's. Do some search here on 17.5" rims. Tires are the same diameter as the ST235/80R16's. ST tires are the dirty little cheap secret of RV trailers, you will never be happy in the long run with them.
There are no 16" LRE LT tires that meet you axle requirements.
Chris