2007 Money Pit - Front Subframe Bushing

[BadMonk]

We just had the transmission rebuilt. The shop said whoever was in there before used the wrong size sub-frame bushing bolts. Instead of getting the correct bolts from Volvo, this indie shop put it together with the wrong size bolts. Now, the car sounds like a tin of hardware over bumps.

So, I got new bolts, plastic washers and metal cups. Easy to do on the rear of the sub-frame. But, when i tried to take out the wrong size bolt with a stack of washers on the front, the sub-frame bolt just spins...like it's stripped. Other than returning to the transmission shop, how can I get the bolt out and what else. I'm not even sure what the bolt threads into. Any advice?

[BadMonk]

Thanks for the replies. So I pulled back the wheel well liner and found this.

One of the previous owners cut the frame and tack welded a nut in place. All the threads in the frame and nut are stripped. I was able to pull the sub-frame bolt out by hand. It was barely hanging on.
Any ideas how to get the tack welded nut out, without doing more damage? It's the wife's car and gets only 3k to 5k a year so just looking to put another nut in place.

[BadMonk]

Transmission shop is going to fix it, weld it up. Better than doing the ghetto fix.