You are going to be impressed with the adapter from Jerry. I gathered all the parts to MS3X my 408, then I scored a G3 hemi, so that will now get the MS3X.
Just an FYI, not sure what you were planning to use for an intake, but I thought simply welding bungs in my M1 was going to be a cost effective solution over the $375 edelbrock. I was wrong. I ended up paying $320 to have bungs welded in. The machinist said the aluminum was garbage and he had a hard time with it. He is a reputable guy too. In the end I would have been better off buying the e-Brock. Either way, it looks awesome!