I'll be doing another one soon but here's some photos of an old one. Even the ugliest front cuts can be saved because the "crimp" is usually ok. If I may, here's how I do them. The "door" cutout is marked in tape or dotted lines.
1. Order your new bushing from RTG right away.
2. Grind the front exactly flat on your big grinding wheel.
3. Make a verticle sawcut, through the top and bottom, from the front almost to the front sight slot.
4. Make a verticle cut on the left side across the receiver to intersect the first cuts.
5. Remove the "door" you've created. Remove the remnants of the old bushing.
6. Clean up receiver and door real well inside. Rust, slag has to be evicted.
7. Drop in your new bushing with the barrel sleeve inside. Time it perfectly, or else!
8. Clamp the door back over the new bushing with hose clamps, tight as can be. Square it up good. Tack it with your heliarc top and bottom.
9. Check for timing. Assure a little barrel "end play". The barrel sleeve should be a little rattly/free.
10. Go ahead and weld it top and bottom. Finally weld the side. Sand, wire brush. The "door" will dis-appear.
11. You can weld around the bushing to the front of the receiver so it doesn't turn. I've found that the welds shrink, trapping it well.
Best of luck...Phil