I did a search and found some pics but not enough info. I need to order new pans for my 66 cutlass vert (finally got it home). Is there a good video where it shows where to cut and reweld? Front and backseat pan are bad so I was just going to order the two halves from OPG without supports. Sound right?

 

There are some decent videos of floor pan replacement on you tube. However, a lot of this depends on the person doing the work. What your welding skills are, type of welder your using.

I just completed floor and trunk sections on my 64 F85. Myself, and skill set prefer using lap welding with a series of plug welds throughout. Cut out bad section use as template with 1" overlay on new section.

Be careful to not cut through factory floor and trunk bracing. !! Factory spot welds have to grind them down and peeled off the braces.
Fitting cut out sections to butt weld is difficult. Some do not like lap welding floorpans for several reasons.

I ordered replacement from Jegs on this car. Their prices are great and the sections were fair for fitment quality. Shop around for sheetmetal. Some suppliers rip you off on replacement metal, when most brands are relative same quality anymore.