Hold up, you welded the strut into the car? :thinking:

I don't see why you need to replace the bushings to fix a bunch of siezed bolts but um, okay. Have you tried using something like PB Blaster to loosen the siezed bolts? Also you may need a press to install the bushings but I figure if you've got a welder handy then you've probably got a few other tools at your disposal.