I'm almost ready to buy a 68 Malibu 307 body for about $700, but I have a couple concerns that I wanted some help with before I say yes:

First - There are "cracks" in the paint where the roof and windshield supports meet (I know there is a name for this area and the weld that is there, but I can't remember the terminology!). There is one on each side, they are nearly identical, and there may have been some bondo applied there at one time. Any idea what might have caused them, and is it major enough to worry about? There are no cracks in the windshield and all the body panels match up very well so I don't think it was wrecked.

Second - Is there a quick way to tell if the frame is straight?

Third - Is replacing a trunk pan easy enough for a novice welder?

Thanks for you help!

A pillar to roof seam common for this area to be cracked. usually GM filled this area with lead to prevent cracking. Should be ok for service.
Frame being straight only way to tell for sure is to put it on a rack & measure. If you know what paint flaking from a bent frame looks like it'd be easier to tell without too much trouble. I wouldn't be the one to discribe this to you. I know what it looks like from studyiing several wrecked cars.
Pretty big job for a novice welder. But Noah wasnt a shipbuilder either.