I would use the hedman 79250 for the BB truck chassis.
I installed mine a few months ago and the fit is great.
I was able to keep all of the stock studs and they slid right into place without jacking up the engine.
went with some 3" pipes/muffs turned out in front of rear wheels on mine.
as far as CAR headers, I think they have been using any BB B-BODY headers on the trucks but have to trim a little off the top frame rail edge for tube clearance on some sets.
IIRC someone posted the A-body TTI headers fit the truck very nice also. but not sure 100%.