Basically, patch panels for vehicles mfg in the '30s, '40s, & '50s AREN'T going to fit perfect 9 times out of 10, and that fact doesn't lie solely with the panels themselves. If you're expecting that, you will be let down. They're not meant to be installed like a "bolt-on" part, the reasoning of which has already been stated above. CPA, as well as many other reputable companies, do not make their own sheetmetal parts. Word of mouth will tell you which companies offer the better panels, and from my experience, CPA has good stuff.
If you're inexperienced with bodywork, namely sheetmetal, patch panels should be the last thing you attempt to get experienced with right off the bat. However, if you are experienced, then I honestly don't believe this post would even exist.
