Are you using 'flare nut' wrenches?
They're shaped more like a box-end wrench but with a small slot in the end to slip over the brake line.
Yes, that's the number one question. I'd gone years without knowing about them, so it's worth checking if the OP is aware of them.
Also, if the current brake line is a fabricated replacement (as old brake lines sometimes are) is it possible the fittings are metric?
The relatively new flex hose between the MC and Booster in my '55 has metric fittings. The usual/standard size wrenches don't fit the nuts but metric ones do. Luckily it's not rusty or stuck.I have run across some brake fittings where the nut size seemed to be metric as no US size fit it. Had to go out and buy metric flare wrenches
bought Benzine micro torch and that did the trick. thanks all