3.0l stroker on the m52 uses an s50 crank, rods, and pistons.
a good alternative is the 2.9l stroker which uses m52 crank, m50/s50(m52 are okay but m50 are "beefier") rods, and s50 +2 overbored diameter pistons.
i was building up a 2.9l stroker myself for my 325is. still have the kit in a box. sold the car to my room mate and he doesnt wanna install it, though ill prob just do him a favor and do it eventually.
anyway. you want to tell him you'll want to switch out the crank, rods, and pistons and have the engine overbored for new pistons. if you find reasonable rates in the USA, ill wager you'll spend $2k-$3k in labor, including machine work.