Why can't you just leave good enough alone?  I sell you that perfect example of firearms technology and now you're trying to fuck it up!

Hopefully keeping a spare or two in stock you can have "fun" with what you have.
keeping in mind, the original vented one was considered weak, compared to the solid version.
Hack & slash all you want!
I don't remember a "black" one...it must have been painted, after "my time"? ('67-'69)

With Dremel, all things are possible.

The scout scope mount gets very hot very fast. My handguard is the solid type and I have not had a problem with "heat mirage".

 The vent may definitely throw extra heat waves your way...but the actual scope mount does that anyway.
 I have done this before with GI hanguards when I put my Scout into a TRW plastic  (GI) stock and painted it..I didn't want to mess up my stock guard so I bought a surplus one and modified it.  All you do is measure the cut dimensions on your original handguard then scribe them out on the new one that you wish to modify.  Make your cuts in the INSIDE of the markings you make, then file finish.  If you run into the vents ( probably likely ) you can build that area up with a fiberglass cloth / acraglass gel mix then reroute your vents before you cut the mount slot.  If you do it right it will look sweet.  Remember to seal all your cuts with acraglass when you are finished.

 Can you post a pic???

Cut to shape, file to fit, paint to match!

I did this for a friend, he had broken the stock handguard. We used a Fulton Armory unbreakable handguard. I cut the hole for the scope mount with a dremel, it was easy.