I just bought a Super 55 S/N 35653-518, spec no. 15-0005.  It runs ok, but needs a carb rebuild I think.  Everywhere I look a Marvel-Schrebler TSX-603 carb is called out but this tractor has a Cater UT 0-995.  Is this a replacement unit??  Two parts stores in my area say they don't show this Carter Part number.  Any help is greatly appreciated