B1 to J1 before the residency - ssa

[ArchivalUser]

I am a FMG and I have a J-1. I would like to know if I would be able to get in the US 2 months, with a B-1/B-2 visa, before the begining of the residency and then change without coming back to my country to J-1( I already have the J-1). Is that possible? As I want to spend sometime with my wife during May.Do I have to say at the port of entry that I am a prospective student? So they would give me both , the B1 for the first month and the J1 for the residency.Is that possible?

Thanks

PS: As we know the J-1 visa alowed you to enter in the uS 30 days before the begining of the program.