Have it clean it thoroughly before having a good shop mag it so they are sure there are no cracks any where \
I've had the bad luck of a regular shop mag a set of 906 heads that they said where good only to find out on the engine dyno that one head had a long crack under the center two exhaust ports between the head bolts and the exhaust ports
that shop did a lot of Chevy and fords but not many Mopars
I've seen probably 6 or more 906 heads cracked there in SO CA