Check out good old SOR 98-462
"(f) is of the “belt” type consisting of a fabric or metal belt, is not a reproduction and was originally designed or manufactured for the purpose of feeding cartridges into a automatic firearm of a type that was in existence before 1945."
Give that 5.56 wasn't around before 1945...links assembled together with more than 5 rounds on them could be more trouble than they're worth!
Henry at Budget Shooters Supply (site sponsor) sells M60 links...check pricing there...