completely rebuild front suspension?

From what I read, a factory slant 6 w/ ac build got the same torsion bars as V8 w/o ac. Then V8 with ac got a step up in torsion bars too. Pretty much every build with ac weight added got a bump up in torsion bars. You should find numbers and clocking to photograph at the back end of the bars.
We can't know if your K member needs repairs/welding. I don't think there is a statistic for that. I can say for the K members I have here, 1 of the 3 needs repair ( a lower arm pivot pin hole and a strut rod hole ). It's a little more than 4 more bolts to remove the K though. You'll have to unbolt the steering column ( 4 screws, 6 bolts, and 1 pin ) to back it off the steering gear box. Then 3 bolts out of the steering gear box for easier K member handling if nothing else.