What model of converter do you have now?
When my converter went bad I didn't replace the whole unit just the converter.
I also up graded from a 55 amp to a 75 amp I did have to retro fit it it but was very minor.
I had a wfco and replaced it with an intelli power brand. Much better unit in my opinion.
but I used my wfco housing and circuits. Took about an hour and a half to modify case and install.
Pm me if you want more info
Consider a "smart" converter with 3 stages.
A smart converter will analyze your battery(s) and give you a better charge. They will not boil the battery dry if a wet cell, and bulge those Gel batteries.
But, you'll need a good charger, opposed to one that's the five and dime model.