Nice projects. I recognize the radial. Its a popular USA design, gasoline fueled, spark ignition. he also offers plans for a double row 18-cyl. She's a big momma.
I'm starting to change my tune about MSM ... a little bit LOL. I'm not sure if USA prices & FX is going up, or some MSM prices are going down. But, at least on certain ordinary alloys & generally small-ish offcuts I've had to purchase recently, the gap didn't seem as horrible as it used to be. I guess the answer is 'it depends'. So always need to do some checking.