273ci thoughts?

Keep the 273 for now... drive it. Don’t tear it apart making the car undriveable for too long. You can get a nice 318 or a 360 from nearly any vehicle up to the 90’s before going Magnum or you can go beyond the 90’s and get a Magnum 318/360. There are subtle differences between the two.

Get this book: “How to hot rod the small block Mopar”

https://www.amazon.com/dp/1557884056/?tag=joeychgo-20

Stock style suspension is cheap and effective. You don’t need a coil over front end.

I also agree with staying with a 904. They are a little bit lighter, and take a little less power to operate. They can be built to be plenty strong.