Purchased a GM Restoration Ecklers Rear urethane bumper. Cannot get the bumper to fit. It measures about 1 inch wider than my original bumper and about 3/4 inch shorter. In order to make it work
would have to squeeze the bumper hard to get it to compress in width
and expand in height.

I have previously purchased both a front and rear Ecklers 1980 GM restoration bumpers and they fit well.

As far as I can determine the car has not had any rear end body repairs and the bumper is original.

Any suggestions on how to make it fit?

 

You have to provide photos. Using hand clamps to clamp it to the body on the inside...clamp it and take pictures. I have a really hard time believing that it is 1 inch wider, etc. The width of the top edge of the bumper cover is determined by the back edge of your rear upper body panel...which is a set distance with NO bonding seams across the top edge. So it being 1 inch wider is hard for me to grasp....seeing how 1978 to 1982 are all the same width.

DUB

 

I sent it back today as I could not get it to fit. I found a tag on the back of my original bumper showing it was made in September 1979
confirming that it is an original bumper. It seems like the new bumper
was either not molded correctly or somehow stored so the center was
compressed which caused the sides to expand.

Expensive experience as the original box got wet when it was sitting
outside my house when it was delivered so was not usable. Paid
Fed Ex to box it for $40 and $65 to ship it.

Anyone else have a problem with a GM restoration 1975-79 rear
bumper not fitting? Would like to find out before I order another one.

 

I have installed more rear bumpers than I can count (both rigid fiberglass and urethane) and I for the life of me STILL can not wrap my head around the issue that you are talking about. It just does not make sense. ESPECIALLY if your rear upper body panel is NOT modified.
All 1978-1982 rear upper body panels are geometrically the same (or at least so close it is not worth mentioning the small amount deviation).
So,,,the feature body lines at the ends of the rear upper body panel is where you set the bumper to match as well as possible and you are stating the the rear bumper is one inch wider ( which just does not make sense)...and you are stating that it is 3/4 shorter ( which also does not make sense.) due to the quarter panels might have some variation to them...but not that much...unless your car has been modified.

Also it still does not make sense if you are referring to the distance across the top of the bumper is 3/4" shorter...and the area on the vertical side being 1 inch longer.

I would have really liked to have seen photo's of your problem.

Hopefully the new bumper will work better...and if your box got wet from the delivery person leaving it outside...you should not have to...or had paid for shipping/boxing of any type. Due to being defective...The shipper should cover that cost....and a bogus wet box was also not your fault. For whatever that is worth.

DUB