The 7H9983 has been replaced by a 4S5755.
The 7H1582 has been replaced by a 1S9397.
Both are available at Heavyquip or Regal and many other aftermarket suppliers as well as Cat.
Get the right stuff, put it together and be done with it. Cobbling it up is just going to lead to more problems. The 17A is a really good unit if built right.