This might be a worthwhile project. Depends if I get enough time on the side to mess with it, I'll try and make a "template" for cutting 2 door Cutlass (81-88) body side molding ends. It's quite weird. They would cut the end of the trim where they wanted it to stop using bird mouth cuts on the ends, and either extending the top chrome line with wedge cuts on some of the NOS moldings, then cut the lower chrome bead slightly shorter so the top folded back to fill in that gap without a cut line on top (best way to put that in words, I'd have to show you), or do it like the factory versions, they would just cut the birmouth out completely, then take another small chunk and cut the fill wedge to fill the end gap. This made the ends complete with a vertical chrome bead on the end. This left a finished end on 4 places on each side of the car. They only did this with the trim ends that faced the wheel wells and the very end, NOT the ones facing the door edges. The front end piece actually ON the door had a slight vertical angle cut to ensure it cleared the fender as you opened the door.
Here's a couple of pics of my 87 showing the angled cut on the door. Never measured the angle, but it doesn't have to be a major one. Don't think it's a 45 degree angle, more like 30-ish.
Here's a crude drawing of the molding measurements and info that may help. I measured 14.5" from the bottom door edge to the bottom of the molding. This drawing is for factory 81-88 Cutlass 2 door body side moldings only. Others may differ. CAVEAT: The factory didn't always measure stuff exact, as if you've ever worked on a G-body you already know this. Your measurements may vary. TIP: Always use a super sharp heavy duty knife or molding cutters and maybe a few dabs of vinyl adhesive for the wedges for best results.