As you know manu created four types of people the Hindu society falls into. If you are a Muslim (Indian) and wanted to convert what cast would you fall into?
P.S. I know the cast system is kinda banned(?) but still widely practiced especially in rural areas.
It's a complicated question. In India, caste is more social than religious, at least these days, and you see caste in both Christian and Muslim populations, although leaders will deny it. Originally it was called varna, and was intended to separate people by their natural inclinations, just as schools might have more than one 'stream' ... academics, practical, etc.
What's banned is caste based discrimination, not caste itself. In that sense, think of it as you would gender or age based discrimination. It's hard to implement though, as communities will have access to situations that will help them remain in a caste, just like money will help a person remain in an economic class.
For newcomers and converts, it's just as unclear, and how you will be seen will be determined by the community you're seeking integration into, if at all. So if you're already a lawyer or a teacher, you'll be widely accepted, a tradesman, somewhat less etc. There are many subcastes, and are roughly the equivalent of occupations.
Caste is not in the forefront of most people's minds at all though. It's there for some, and varies a lot by community. In my trips to India, I didn't notice it at all, and very rarely over here. Once in a blue moon I have encountered a casteist person, just like once in a while a racist will show his true colours.