Question

Are lengh mass ton customary or metric

Answer 1

I am pretty sure it is customary

Answer 2

Length and mass aren't measures of unit. They are just what is being measured. So, they are neither customary or metric. Though, there are customary measures for length and mass, there are also metric measures for these both. 

Length customary: feet
Length metric: meters

Mass customary: ounces
Mass metric: grams

These^^^ are only some examples, there are more measures of units

Though, ton is a measure of weight in the customary system of measurement