Matt, there isn't enough meat on those inserts to drill out and tap with a helicoil. In addition, both sides need to be aligned and brazed in place using an old fulcrum pin so both screw faces are correct distance apart. Even a tiny bit of misalignment and they will not screw back together. In my case I determined that my MAPP Gas torch could not get hot enough to undo the brazing that was done on my wishbones when the bushings were previously replaced. At that point as JAck Laird commented, " Sometimes the best tool in your restoration process is your credit card."
I did play with a set of wishbones out of a scrapped '69 and found I could easily unsolder the bushings and remove them. The set I have out of a later model Spridget that I had installed in Bugsy were predrilled for Sway Bar and overall were much heavier construction than earlier wishbones. I know they were rebuilt at least once as there is a rebuild tag on them and one came with a rear grease nipple fitting.
Apple was able to supply bushings for $9 a bushing + shipping. They will R&R both bushings, check wishbones are not bent and straighten if needed, and return with approx. 5 days of shop time price quoted was $95 per side. After fighting this one I made the decision that my Credit Card was the best tool here.
I did discover that both of the wishbones I pulled off of a scrapped 69 were totally unusable as cores. One was totally cracked around the fulcrum pin with < 50% of the metal still remaining on the wishbone and the other side was totally twisted and bent. In both cases it appears that the kingpin siezed and simply tore and cracked the wishbone.
If you decide to order bushings and do this job yourself, order an extra fulcrum pin to use as a sacrificial pin for fitting. Heating the wishbone to reinstall bushings ruins the temper of the fulcrum pin. I did find this piece of advice as well.
Before commencing assembly the bottom trunnion should be bedded into the wishbone bearings; it is a tight fit and is usually impossible to fit if the following procedure is not carried out: Hold the wishbone pan in a bench vice so that the bottom trunnion access hole is uppermost, (vertically so the trunnion can be screwed down into the wishbone). Thoroughly lubricate the trunnion pin with grease and insert it into the hole. The next job is to screw the trunnion into the wishbone using the same action as used when tapping i.e. 1/2 turn forwards then back off by 1/4 turn. DO NOT USE A SCREWDRIVER FOR THIS; the trunnion pin is case hardened and the use of a screwdriver in its slotted end can result in the trunnion shattering, so rendering it useless. Instead of a screwdriver use a piece of mild steel bar which is a good fit in the slotted end of the trunnion. This way you can provide more torque evenly, without the risk of shattering the trunnion, the bar may bend whilst in use and require straightening several times, but this is much better than scrapping the new trunnion. Once the cotter pin slot is visible through the first bush you can use a 1/2" spanner on the flat of the trunnion, which will allow the safe application of even greater torque.
Good luck, Bugsy's wishbones will go out today for rebuild if I can find the right sized box