Fitting TTi headers on a 273

I've been using a big flat file, since the 60's. (and sometimes a welder and/or grinder/belt sander)) to true and change the angle the headers leave the engine, by filing the flanges.
It.s no big deal, it's a last resort for gaining clearances, but used to be absolutely nec. to get the old headers to seal.

It takes very little material off a flange to get 3/16 on a lower tube, or the collector.