seatpost clamp replacement

I have an old (~20 years) steel bike with an integrated seatpost clamp.
The clamp is just two "ears" brazed on the tube, one ear on either side
of a slot in the tube. I can't see any problem with knocking off the
ears and replacing them with a separate seatpost clamp. Can you? How
would you recommend knocking those ears off without messing up the seat
tube?

Here's a few more details. Until recently, the bike has not had any
trouble with the seatpost slipping. I took a closer look at it over the
weekend and found that the seatpost clamp was bottoming out; the two
forementioned ears were touching. So I put a beer can shim around the
seatpost and tightened it up again. Even when the ears were touching,
the clamping force was not sufficient to hold the saddle from pivoting
in the frame.

The seatpost is well greased. It's a 25.6 mm post in a pretty cheap
frame, and there is very little free play when the post is inserted and
the clamp is completely loose (i.e. the seatpost fits pretty well). I
don't see visual evidence of cracks in the seat post anywhere. I suspect
the ears are coming off the frame, and more shims will just make the
ears bend a little more... maybe that's how I should remove the ears.

Thanks for any tips.

--
Dave
dvt at psu dot edu