Advise/Pointers on enlarging hole in hood

Hi Guys,

Next project coming up on my 64 Valiant is enlarging the hole under the scoop in my hood. Never cut metal before and have some questions. The challenge is the scoop should have been installed a little further back so scoop is not centered and engine is tall though I will be working on that too.

As you can see the hole was cut very badly and due to the engine height I am currently limited to the size of air filter I can put on the car. I want to enlarge the hole. I am going to remove the spacers on the engine to lower it a bit as I would also like a taller cleaner in addition to a larger one.

Again....this all new to me so any advise even if it seems completely obvious is helpful to a newbie like me!

Questions:

1. Can I safely cut through the cross members in the hood? Will this cause any issues?
2. Do I just need a reciprocating saw and grinder for the job?
3. Once cut what can I put on the newly cut edges to prep and protect from rust?
4. Does it have to be cut in circle or can I do more of an oblong/ rectangle shape for more air? Can I cut most of the metal under the scoop? Or is this frowned upon?
5. I tried to find a good video on YouTube but didn't find anything good about this project. Does anybody have a good link?

Here are some pictures
Yes....first thing I did was swap out that triangle of death....


About 12 inches. Can I cut those cross members under the hood?


You can see how tall the engine is though I am removing the 2 inch spacers.


This is the largest cleaner that can fit at the moment 10 inches


Scoop from outside


Here is the car...