Cut the firewall for 2 bolt Master Cylinder!

I just drilled two 1/4" holes in the middle of the 4 holes. Didn't weld, just bolts. The 4 studs are part of the brake pedal bracket and just pass thru the firewall. I didn't cut them off. I used a big washer to cover the opening. Using a new MC for a ~99 Breeze. I have read that MP MC's are just Dodge truck ones you can buy for $25. I knew you can buy the adapter plate for ~$45, but too much of that and my $1000 Dart soon costs >$10K.