The brace that I used is the same one (I believe, but not 100%) that
www.shakerhood.com has. I have to say that I was not impressed with the fitment. The brace that Harms' is selling looks to be far superior, granted I have never seen one up close.
There is tolerance when installing the brace. I chose to leave about an inch of the original brace underneath the new reproduction. Once the old brace is cut down and the center section removed, the new one can be test fitted and adjustments made till it fits well and is centered. There are enough contours on the brace and left on the original that it will self center pretty close. At that point I tack welded the new brace in and traced the hole. The hole will be the same size as the one in the new brace and should be in the correct location after the above is done. The tack welds were broke, the hole cut, and then the trim ring needs to be tested against the hole and adjustments made to the hole to fit the trim ring. I assume this will just need to be done with the aftermarket trim rings as little tweaks only needed to be made to various areas. (Harms’ trim ring might be a lot better too.) Once you are happy with the hole, flange the edge, permanently install the brace, drill the hole for the trim ring studs, and install the trim ring.
If you are curious about Harms’ pieces you can see them here:
www.harmsauto.com