I think they also did away with the reduction boxes on the chain case. The same pump, the same engine. They only made them for a year ot two.I think they are the same,the 743B model was the last of the series when they made the transition to the 753 C series.Maybe a couple of features like the 743B engine stop was on the key instead of a pull cable.I had the last of the 743B model which was a 1995,in Australia anyway.The 753 had already been out for a couple of years by then.
The 743B also had the early 753 lift arms and the bolt on axle caps .I think they also did away with the reduction boxes on the chain case. The same pump, the same engine. They only made them for a year ot two.