You'll have to make sure to weld that in good because it's your support for the whole vehicle in a roll. Is yours rusty or are you just thinking of swapping them due to the old roll over damage?

Not sure how your rig looks but unless you plan on entering shows with it then I wouldn't worry about some damage. I know alot of guys that will spend a fortune on making it look good with chrome and all these gadgets but when it comes to being functional it's not worth a crap.

Get it running and get it tough and then worry about the shine on the paint. Nothing I ever own is shinny. I'm in the process of getting ready to restore the LJ but it will be a first and the only reason is that I've got the 413K and I don't want to wheel the LJ.

If you are going to attempt it then take your time and measure a whole bunch of times. When you cut the replacement piece make sure to make it a hair bigger and then trim to make fit. IF you cut too much out then it's hard to fill gaps.

This is completely off topic but I've always had the dream of grafting the sunroof portion from a 2 door onto a 4 door.

  i have done  chops before   for the most part 1950 chevys and fords and a merc . but their metal is much thicker then this . not to mention rolling one would well you get the idea .
 myself i think  doing a 8 pint brace would be a must  on the donor .
 near as i can tell , the stregth comes more from the shaps  over actual thickness  of the  material .
 thus once cut , im thinking  she would warp fairly easy ..

as to the 4 door . you know its funny  becouse i was just thinking  while looking at whats left of the 95 donor .  it would make a great little soft top blazer .
 simply weld in and french the back doors  take th top off right at the level and then put a full soft top on it .
 

Overall it doesn't look bad, at least not from here!  If you are worried about safety, I'd consider putting in a roll cage, might be easier then chopping and reattaching the roof.

2nd the roll cage, if your gonna put the work/money into it, might as well REALLY be protected.

 well i can full understand the  "really be protected "  idea . but somehow ,  i just have a hard time with a roll cage  inside my daily street driver LOL .
 though most certianly  if it came down to needing it , it would be better then the original design lol

can you add some plating where the cracks are? Alot of times some plates welded in can really help the situation. A roll cage in every vehicle would be nice but for a DD then I personally think it's a waste of time and money as long as this is not your hard core trail rig.

I've never had a cage and never had my rigs over. I don't wheel rocks or areas that are at risk for rolling.I've laid it on its side but just drove out of the crack. Slow and controled. A cage has to be attached to the frame and if it's not then it won't work right.

plate from the inside and out if you can and then have fun.

Well, I would put a cage in it, and its cuz of being drug around to accidents all the time as a kid, and seeing what happens, especially to small vehicles like these, and I think a roll cage is a small inconvenience.  That being said, If you weld a couple plates around it, its gonna prob make it stronger at that point, than it was before, and its much cheaper, as far as tearing out the frame and putting a new one it, I still think you safer and better off with just putting a cage in, hell be easier too. but thats my opinion.