The TH350 and TH400 converters are interchangeable. The TH400 converter has a wider bolt pattern because it typically was matted to a 168 tooth flex plate and the TH350 converter has a smaller diameter bolt pattern and was typically matted to a 153 tooth flex plate. Most after market flex plates now are dual bolt pattern to accept either converter so starter change is not necessary.
If you have the other carb you could change it to see off it cures the issue however, those seem to be classic converter issues. The converter could just be bad after the years of sitting.
If you have the other carb you could change it to see off it cures the issue however, those seem to be classic converter issues. The converter could just be bad after the years of sitting.
