I have a 1983 150 with the 300. When I bought it, the EPA stuff was disabled and/or removed. I had to replace the carb and getting the geometry of the AOD TV cable has been problematic. I wanted to try removing the inoperative EGR, add a piece of sheet aluminum (beer can) sandwiched between two gaskets to cover the open port. What may be the ramifications of going spacerless?

 

The thin aluminum sheet will not endure - it will eventually fail. A "better" solution would be to install a cup plug in the EGR supply port...
...or keep the EGR functional.

 

Have you looked at a pre egr spacer? They don't pop up very often, but they are still out there, more common in Canada I think.

 

Just drill and tap the EGR hole in the spacer for a plug.

 

Some have used a spacer like this:

Crown Automotive 53000616 Crown Automotive Carburetor Insulator Spacers | Summit Racing