All it takes to tack a bracket into place is holding the button on the MIG gun for like 3 seconds. Just a small dot to hold it in place so it won't move while you cycle. If you can barrow a unit, great. You won't need more than a few dollars of wire and gas at most so a pack of his favorite drink should cover it. You'll need gloves and a welding helmet too.
I don't know what you have for tools, but I highly recommend my 12amp Metabo 4.5" grinder and Walter cut off wheels and theirhighEdit: low grit flap wheels. A face shield is a must.
2 floor jacks make the job SO much faster to cycle the suspension than just one.
All that, along with a mini-sledge should be enough for you to mock up the mounts.
By the way, I'm not seeing a 12 amp Metabo grinder in 4.5". I only see the 12 amp in 6" and larger:
https://www.metabo.com/us/enus/tools/cutting-sanding-milling/angle-grinder/angle-grinders-o4-1-2-6/
Is the 4.5" more ideal than a 6" for a project like this?