stock 68 Buick 350 in a 65 Skylark, no A/C, 4-speed. I’m thinking no, but just thought I’d ask. These were in a ‘68, thus my concern. https://minneapolis.craigslist.org/csw/pts/d/buick-350-parts/6410340237.html
If ( if ) those are KB 350 headers their older catalogs did say they would fit 350 in a 65 n newer car . Can't remember the part number . I never used them so can't confirm . Plus some older parts catalog listings were not very accurate and allowed for installation mod's . I would be cautious . Some of the guys on here say the hookers fit pretty good .
If you don't mind cutting and welding, for $150 bucks for a set of sbb 350 headers you can't really go wrong! You can probably get the guy to take less as well for all the dents in the lower tubes that would need a welder to fix anyway. A torch(an oxy-acetylene torch would be the better one to use vs one of those hardware store bottled propane disposable torches) works really good for moving the tubes as well. I had to cut off a tube and had to heat up the tube where it was still attached towards the bottom and heat it up red hot around the area I wanted to move it, to re-attach a pipe that was out of the way of the steering. The torch works great for dent clearancing as well if just a small dent is needed to make them fit. HRM did a video with an engine on the dyno and hammered the headers more and more after each dyno run to see how much power the engine would loose. What they found out with the headers on both sides severely smashed is that it made very little difference in performance! So don't be afraid to make a dent here or there for some clearance. If you're all right with doing a little fabrication, then you shouldn't have any problem making them fit if in they are off a bit.GL
Years ago I read an article about repairing header tubes by blocking off both the flanges and the collectors, tap in an air hose fitting in the collector block off plate, plug an air hose onto it and heat the tubes up with an acetylene torch. I've never tried it but it seemed to work in the article I read. It's probably more effective on dings and dents rather that almost completely flattened tubes like those on craigslist but it would still be worth a try.