The .63 A/R turbine housings crack, but they crack far less than the .48 A/R housings and they don't usually get much worse. The smaller ones crack really badly, and I've had them where the snail actually cracks through and chunks of it move around or even get lost. The bigger housings seem to crack pretty early to relieve stress around the wastegate hole and then are usually pretty good.
Something I just remembered is that your .63 housing is one of the early ones that uses a steel gasket between it and the manifold. From about '83 on, Volvo has used that stepped circular flange arrangement that you'll find inside the turbo you pulled from the 740. I had that '90+ manifold planed flat to use this turbine housing, so you can't use the 740 turbo on it, not even with a gasket. If you don't have another manifold for your smaller turbo, you'll need to find one.
You can still see the radius they machined into the base of the step to relieve stress risers, but the manifold is flat.