Headers for 1969.
 

I am working on an engine swap. I am planning on putting a 350 in place of a 327. It currently has exhaust manifolds. Are there headers that match the sizing so I would be able to avoid getting into welding equipment?

Factory small block heads are small block heads. There's no cross-fit issues or anything you need to "match" to.

You might consider keeping the stock exhaust manifolds because they are zero maintenance. Headers give 20-30 more horsepower, but at a cost. Exhaust leaks, fitment issues with ac compressors, spark plugs, and standard transmissions.

I can vouch for the transmission fit issue. I am converting from auto to standard and am in the midst of dealing with zbar interference with existing headers. I will probably get headers designed for standard tranny , ac and power steering box which seems to be the main fit up issues. Let your header supplier know all the details of your specific car. You will have to get exhaust shop to match exhaust system up to headers which will require welding in some capacity. A hydraulic clutch is an option for flexibility of installation and addresses some fit up issues. I am a do it your selfer and it has slowed my timeline to complete by a couple of weeks.

I like headers but they do come at a cost as mentioned, but the problems can be sorted out if you want to take the time and deal with some frustration.

Good luck!