Just thinking out loud, but why is a 3/8 dovetail desirable? [I suggest the size of the dovetail is not very important]
Why do you want to solder on a ~$350 barrel that is already finished, in order to use a $5 front sight? [I would choose to modify the sight, not the barrel]
If you do not trust yourself to make or modify a new sight [at most an easy half-hour job], why do you trust your workmanship in modifying a $350 barrel?
Please understand I am not in any way challenging your skills, but as a teacher I am used to the Socratic method of asking questions. I intend this to be helpful, not critical.
As an "apprentice" 40+ years ago I learned to make whatever parts I needed. But I had to escape the conventional mindset that you buy everything, before I really began learning.
Wayne [Stoner creek] is giving you really good advise based on a lot of experience and skill. When he speaks, I listen!
I hope this helps, and that you keep posting your progress.
Carl