If you are looking for a "Driver's side" factory header - and you're talking about a stock version - I hate to BREAK the BAD news to you - but:
A - Most will be welded up - and it's not "junk" if they fillet the welds in an overlapping pattern at the junction that breaks so frequently.
B - If you get one that has not been welded it will either be:
1 - New and need to be welded up at some point in time
2 - Used - and Need to be welded now
or
3 - Used - and Will need to be welded in the future.
Perhaps you have seen the weld repairs and thought it looked sloppy or like overkill.
In most cases, if they are done properly, the welder is skilled, they will either overlap their welds, filling in the junction area - or - add a gusset in the "Y" area and weld that.
Either way, most or all eventually have to be welded.
Unless you are looking for a set of low mile, take offs that someone removed when new, or close to new.
If that is the case - get out the credit card.
Lots of threads on here about the repairs.
http://www.turbobuick.com/forums/threads/sticky-how-to-header-repair.330187/