i find it easier to remove the air hose from the air cleaner to the amm, then reach down and unbolt the lower u joint at the steering shaft end, then let the lower u joint come off the car with the steering rack.

off the car, it's easy to pull the lower joint off the old rack and install it on the new rack.

the groove pattern on the steering shaft is simpler and easier to engage than the groove pattern on the stub on the rack.

if you take off the u joint and look at the two ends you'll see what i'm talking about.

inyour case, since the rack is off the car already, you might remove the lower joint from the steering shaft, install it on your new rack, then install the rack/u joint assembly on the car.

put some blocks or jack stands under the car, and set the rack on them so you don't have to deal with the weight of the rack while setting it in place. check the alignment of the u joint and the steering shaft, and tie off the steering wheel so the steering shaft doesn't move on you.