In my searching, I've found several options for a smog system (which I've never had on my car since purchase in '76):
1) A reproduction system for around $700 (advertised lots of places)
2) A 100% original '69 system, with hoses, clamps, etc wtih good dates for my car, for a bit over $2000.
3) A combination of 'original dated' parts-including hoses (only repro are tubes and pulley).. for something under $1000.
Since I'm not even sure I'm going to install it, but want to get one to *store away* for 'whenever'... I have
decided to go with option 3.
I played with early Z28's for 10 yrs or so (from '68 til late '70's) before I even *saw* one with a factory-installed SMOG. Chevrolet KNEW that Z28 buyers were going to install headers, thus they put no effort into making the factory exhaust manifolds more efficient (rams horn manifolds are much more efficient). 302's do not run great without headers, so although I'm probably going to buy a smog system now, I will likely install the ceramic coated headers I have, but keep everything else original.