I got a response from RebirthAuto. They claim the correct adapter pattern was machined for my transmission. It seems there is some confusion on the 5-speed transmissions that were used in E21 BMWs in the early 80's. I have the transmission that is listed for a 1983 E21 5-speed, which is model number 240 manual transmission. From the pattern of the adapter that RebirthAuto provided it appears they patterned after model 245, another 5-speed transmission used in E21s. The problem is model 245 5-speed transmissions were only used up to 1982. Starting in 1983 and later BMW started selling cars with the model 240 5-speed manual transmission. The issue with the bolt pattern not lining up however, probably is a non-issue. I reviewed the video I shot during the removal of the ICE. Here is a picture that clearly shows the bottom of the engine was not connected to the transmission (because there is nothing there). There was a dust cover plate that was on the bottom of the transmission where the miss-alignment is with the adapter. So those bolts do not carry any of the transmission load. The remainder of the bolts that are connected should provide all the support needed for the adapter. So I will use this adapter as it is. The next step is to pull the motor and transmission assembly back out of the car so that the flywheel and clutch can be installed and the motor rotated 90 degrees. After these changes are made and once I have everything bolted back together I plan to spin the motor and transmission on the bench, before putting back in the car.