anyone welded up spider gears before??

Just about any late 80's -90's box Jeep. Most have 3.21 or 3.55 gears. The axles mount on the frame with coil springs and trail arms so you'll have to weld spring perches on. You can mount the assembly on the car and take it to a shop to weld. A B-body rear is only about 2 inches wider than an A-body per side. The front track on an A-body is 57". The rear track on an A-body is 55", a B-body is 59". I have a friend with a Duster running a B-body rear with 29550R15 tires tucked under the fenders but he does have the spring relocation kit installed. You only need that if you're going to that large a tire. I spotted a '74 Duster in the boneyard today with a 8.25 axle but it only had 2.45 gears. I might grab it just to have.