With all inner replacement panels in place, it's important to double check the alignment before tack-welding.
First order of business is to tack only the places where the new panels connect to each other and to the car itself. Remember, it's very important to allow space between tack-welds so the sheetmetal won't become hot enough to warp. This is similar to stitch welding. It's a good idea to leave 4 or 5 inches between tack-welds.
Here we can see the package tray and trunk hinge support welded to the inner fenderwells. Every place there are factory spot-welds will need to be re-tacked, even in those hard-to-reach areas.
A lot of the work is going to take place inside your car. These panels really fit and look great. Not much modification is needed here, just don't forget to weld in all the required places.
If you look closely, you can see it was necessary to replace the edge of the trunk floor where it meets the inner fenderwell. If the sheetmetal is too thin from years of rust, it will be important to replace it so the spot-welds will have a strong base to hold to. In this case it was only necessary along the edge of the floor.
At this point it's time to line up the new quarter-panel. Many clamps and a few other hands will be helpful at this stage. Re-check and then re-check the alignment again. Very, very, important!!!
Once you are happy with the alignment, tack-weld only in a few choice spots, so the alignment can be re-checked before you get too far. It's also a good idea to leave the clamps on until the panel has been fully welded on.
The funny looking Vise-Grips are perfect for this kind of work. They allow you to tack-weld between the pressure points of the pliers. A hammer and dolly will also be helpful in persuading the sheetmetal to line-up perfect. Again, place each weld away from the previous one to keep the sheetmetal from becoming too hot and causing warpage. If needed, it is a good idea to have a bucket of water and a rag close at hand to cool the tack-welds.