if you do it yourself it makes zero difference.
the idea that every cracked housing makes a junk turbo is ridiculous. please don't persist with the notion that the crack is a total deal breaker.there are hundreds and hundreds of vf39s out there being used every day without boost creep issues and without having a bigger wastegate flapper installed.plus the 39's are notorious for boost creep unless you go through the trouble of a bigger waste gate...which just adds to the cost of the turbo setup as a whole.
most of the turbos that DO have creep issues could be solved with judicious exhaust housing porting, which can be done in all but the most seriously cracked cases.
most vendors don't like you to know that, though--there's no profit in teaching people to do things themselves and not waste money on new parts.