Actually, J arm or A arm has nothing to do with it. It's early style brakes and late style brakes. Early style was 87-89. Late style was 90 and newer. 1990 was a J arm Banshee with late style brakes. Spindles are interchangeable between all years of Banshees, BUT, you must use ALL of the brake components from whichever style of brakes you have. Spindles, calipers, rotors and hubs. Here is a pic of the early spindle. Notice that the caliper mounting ears are about the same length.
Here is a pic of the late style spindle. Notice that 1 of the ears is much longer than the other.
He parts out a LOT of Banshees. You will definitely get something. It may be bent, rusty, scraped up or rattle can painted. There's a reason he's known as Rattle can Ray. If you wanna roll the dice and buy from him, go ahead. Just saying, there are much better sellers out there to buy from.