71 Dart Swinger 318 Green Go Restoration

So got the 318 torn down but had many, many overheats. Hole clear thru cyl 1 and 5. Rest of them bluing in the same locations. Decided sleeving was not going to be cost effective. Found a Dec 71 block that was to be rebuilt but builder had issues with that one and without telling me, rebuilt and sent me a July 74 long block. I immediately called them out and they are trying to find a late 70 or any year 71 to build and swap the 74 out. My question is, are there any differences in 70/71 to 74 blocks. Not sure if I should keep this one if they can't find a replacement. Thoughts?