I have opened up a number of early H&R bases for the newer production NEF/H&R's but never anything for a T/C. I prefer a silicone carbide paper though, not typical wood working "sand" paper.
Besides the hole spacing is wrong. Are you intending on drilling and taping for the different T/C holes? If so, I will assume its for the additional hole and extra strength. If this is the case, note T/C chooses to use very small screws, do you self a favor and open up the holes for #8 screws and enjoy even more strength.
This has been done for years and years with the heavy recoiling calibers in the Contender. I had to do this on my 357 Herrett. It sheered the smaller screws clean off!!!
CW