While you will need to look at ever possiblity, I wouldn't think your problem is caused by a head gasket. There also are more ways other than welding to fix a cracked block. If that is the problem.

With the price of orginal Hemi cars going through the roof, and if this is the orginal Hemi block the last thing in the world you want to do is throw it away. Any number matching Hemi, that is all numbers orginal to the car, is worth 10's of thousands more with the correct block.

The first thing is to determine were the problem is. Then and only then can you make a choice on __How to TRY and fix it. Welding is one way but it is only one way. Good luck!!

Roland