Those Efco 400-series brush cutters came with at least two different carburetors: a Zama C1S and a Walbro WT. There may have been more types used.
The Zama rebuilds fairly well, but those Walbro WT's and WA's are of the hit and miss variety: don't lose sleep over them if they do not respond well to a rebuild. There are Chinese carburetors that can be used as bolt-on replacements with just a tiny bit of tuning.
If all it needs is a carburetor rebuild and new fuel lines, run it until it breaks down then.