yes, i would think so lol thats my plan.. there both an amazing cichlid. but they grow farely big so you might get a couple of years out of your 55gal then you might want to up grade.
Maybe you could short term, but a grown GT will be far too big for a 55gallon let alone a grown JD and GT. A grown JD can survive in a 55gallon but I don't think it would thrive. That's the bare minimum suggested requirement for a grown one.