What is the best size camshaft to go in 86 Chevy c10 350 engine Im thinking 2 stage just want a good rumbel and hopefully add few extra horsepower. Any takers?

You're very limited unless you want to change valve springs and make other changes, and what gives it the "rumble" is what's going to make it not pass emission testing (if they do that in your area and go back that far -- 1986 -- on vehicles they test) and will destroy your gas mileage. Something like a high energy 252 or 260 from comp cams or anything with similar specs would be good for the application you describe, it will have a fairly smooth idle, a little more power, and probably won't destroy your gas mileage, again, make sure it will pass emission testing for your area or is C.A.R.B compliant in which case it will pass anywhere in the USA, I'd talk to the camshaft manufacturer of your choice, they can tell you what you need to know, I doubt if the stock valve springs will handle anything over .450 lift if that. If you run too big a cam and get into spring binding you'll bend push-rods or ruin the new camshaft or both, and some of the mid 80's and into the 90's small blocks used a shorter spring on the exhaust valve that was not meant for use with aftermarket higher lift cams, something you should check, or, if you don't know how find someone who does.