My 270 had thru-holes for the data plate. When I rebuilt it, I ended up using these brass nails from McMaster Carr. The head profile is pretty close to the factory rivets.
I cut them a little longer than the combined thickness of the data plate and the block, then peined them over on the inside. I also coated the ID of the holes with epoxy, to ensure that there would not be any oil seepage.
The only downside is, like many things with M-C, you have to buy way more than you need - in this case 25.
I'll never use all of these in my lifetime. If you're interested, PM me your name and address and I'll throw some in an envelope and toss them in the mail.
