thats where i need to get some clarification, will bead blasting leave the exact same appearance that was there originally , if not then i would spray paint it so it is correct
Original? Well, right there that is a little controversial? It really depends on the original finish on YOUR manifold.
Some had very rough cast finishes. Some almost shinny like a pressure cast item does. I'm convinced they ALL had the COBRA highlighted.
I would rephrase the question and consider it a question of what the predominant majority of the knowledgeable expect the manifold to look like. In other words, take the advise of someone like Bob Gaines or the equivalent as to what is a "pretty good" representation of what the original finish was. I don't think that you will ever get a 100% agreement or even close to that of what it should look like.
You CAN hurt them a little by using the wrong blast media AND the finish on something like the Blue Thunder manifolds confuses things. It's pretty but hardly what the originals came out looking like.
IF you decide to play with different media in the blaster, protect the machined surfaces. That is really a PITA but I think worth it.
Personally, and I'm gonna' get flack on this one for sure, I like the Black Beauty SANDBLAST media followed by a wash with the HEAVY DUTY, smart your eyes acid wheel cleaner. It's going to make it look like an Edelbrock finish and similar to the Blue Thunder. Both REALLY nice finishes.
That will get rid of a lot of the staining put into the castings by years of grease, grit and spilled gas BUT (and this is a BIG one) it may reveal casting flaws like porosity in the castings that you never saw before or knew were there? So that's kinda' a can of worms.
If you are a perfectionist, you are probably better off sending it to Jim Cowles? He's a PITA too but you need to remember the same thing that makes him difficult to live with is the same thing that makes his results exceptional?
Definitely stay away from paint though. You do not want to go that route.