273 valvetrain question

Well, at least, a head R&R is not nearly as challenging as rebuilding the bottom end. There are no precision measurements and setup work that I can think of in the cam change and head R&R work. Though timing in the cam with a degree wheel would be wise, and some might consider that precision work. But it does not involve machining and measuring in thousandths of a degree.

You need to be draining the block for the cam change anyway. And you can check the valve to piston clearance with the new cam if you do this.

(BTW, I have a 09 Challenger too....)