Engine is in...need to shim driver's sideside

I am experiencing the same issue with #7 tube hitting that steering sleeve. Is there anything to be careful of when ' trimming' that sleeve ? How much can you trim off of it ?
Thanks
I actually ended up modifying the header....used a nice heavy piece of pipe against the header and put the hammer to it....that put a nice smooth radiused clearance on the header.
Looks clean...almost like it came that way.

Jeff