Any MGB steering arms can be used as is, as long as they’re in good shape.
The rack needs to be from 1959 – 1970. I don’t know about left and right versions since my steering wheel is on the left.
The engine does not have to be out of the car, nor does the cross member. I loosened the four cross member bolts, removed the front two and tilted the cross member so that I could undo the steering rack. I was using a lift for this and supporting the cradle with a transmission jack and another pair of hands. The rack come out and the adapters go onto the cross member brackets and the new steering slides into place. Once I got to this point I thought I was going to be home quickly…not quite. There is some fussing involved, some twitching and tweaking but nothing really serious, just aggravating. The steering knuckle appeared to be 1/2" short of fitting onto the rack. You have to loosen the expansion tank and the steering nut so that you can push the steering rod to the front. This does make up that short difference but then you have to adjust the outside metal tube (steering column is inside) so that the clamshell doesn’t bottom out on the dash. It all goes back together just fine.

It took me about two hours, maybe three, to make the change. Aligning the front is much easier and so much more accurate. A good tape measure alignment and the car goes in a dead straight line. Bruce