Thoughts and prayers for you and the family . Like all the others have said, things can be replaced you and the family can not. If you need a kit or two let us know I have a few Mopars I can send your way .No cost to you.
H code says 351 that does not have to be the Cleveland . If it was a Mach 1 you would see tags or strips on the outside. Inside the door panels would have a marking also If I remember right.
If you just going to drive it and enjoy it get a roller 5.0 with a 5 speed .It will be cheaper in the long run and will get down the road fine.
If you put bigger hole in the upper part you will have slop to make the top straight . Just turn the engine over , put spacers under the heads so the tops of the intake are on the table. Then just fill holes with glue.
Just as hack-n-whack said try and make your own windshield .You can always use a clear two liter pop bottle for your glass. It will flatten out once you cut it.