How much trouble to remove old set of headers and install new on 69 Big Block?

I have a '70 so things might be a little different. The passenger side is extremely easy to remove and re-install but the driver side is the exact opposite because of the steering shaft. I put my headers on when I installed the engine so there was no hood on the car and my hoist was still bolted to the engine block. I raised the engine with the hoist until there was enough room for the header to be slipped into place. Assuming your car is together I would remove the drivers side motor mount bolt, remove the nuts on the trans mount and lift the engine via the oil pan (use a floor jack and a block of wood). You may end up having to remove the passenger side motor mount bolt as well but I would give it a try with it in place. Also, I find that the higher I get the car in the air the easier it is to install the headers, just be safe about it. Good luck and let us know how it goes.

Also removed headers from below with car on stands way up, and motor lifted up. Old ones o.k. but rusty. Hate to put them back on.

depends on how easy those bolts want to come out, had a stud snap on my friends 92 iroc-z, so if your headers have never been removed you could be in for some fun. On my smallblock the only way to get hte drivers side header in is from below with the car jacked up pretty far. Passenger you can pull from above assuming the starter is out of the way. 4spd car will need to zbar removed..