This is a B.O.P 8.5 differential complete drum to drum. Has a posi and 4.10 gears. I went through it several years ago and bearings and gears are perfect. Only reason I'm changing it out is because I have a done Moser 12 bolt sitting around. I will deliver to the Nationals, but it must be pre-paid first. I do have it on a few other sites $1000 and it's yours. Will Not Ship