I guess I am not shocked a cheap, off shore bumper does not fit.
It fits the knock off body shell perfect. They are probably stamping the bumper and them punching the holes. The original tooling would have produced the whole part with one crunch of the dies.
I work in sheet metal stampings and have since 1978. You would have a multiple of dies to get your end result for a bumper or any other body part. Usually no less than 4. The problem lies when off shore companies eliminate the die stamping processes and do some things by hand or not at all because dies are NOT cheap or they don't spend the time($$$) making sure their end product is "dead nuts on". Here in the USA our ave die cost per die is 250-300K and we have been working on getting that down but will never compete with China for a number of reasons and one major one is material cost on the onset. Our raw materials cost us more that it costs China to make a die including their material cost the last time I went through the cost meetings.
One good example were the stamping of "full" 69-70 Mustang fastback quarters for a long time before dynacorn came out with a real full quarter. To get a factory stamping the 3rd or 4th operation would flange(tuck) in the lower rear quarter for the drain design. Repos never had that. You got the draw die shape which cannot "tuck" so the trunk drop off never fit and the flange sits way too low and sticks out like a sore thumb.
On new dies we do "first panel scans" and score out panels. What is off due to spring back or bolster flex is digitized and sent back to die design/engineering to correct. We are finally with new technology being able to predict better spring back and bolster flex to the tune our first panel score are much higher. 90 plus is what it takes for a buyoff panel. We have hit a few panels in the 90s the first time in the last year. Drives down iterations and cost and ups advanced die delivery time(BIG deal) to assy plants. That is what we need to do to survive as a UAW Die shop inside of GM. Because of this we are bringing more work back inhouse this year and hiring a lot of Die makers.
Usually you have a draw die, first trim die(direct). second trim/flange, cam trim cam flange and pierce. Sometimes you need 5 dies to perform all the tasks. Piercing holes are usually done in the last die after the panel is "set" after flanging. Variables to this process is why we have die designers and die engineers which we work with in our facility. I'd post pics of all the operations(planning showing all dies and what they do) but don't want to get fired. This process can easily be found online I'd think. Gary