Heater & Wheel Well Removal

[KyleSeal]

So I broke the lower connection to the heater core while trimming the rubber lines. Decided to go ahead and replace it or fix it, not sure yet, but I started to unbolt the housing and realized the bolt underneath is very difficult to get out, so I tried unbolting the wheel well like people suggest, well all bolts came out besides one, and it just turns n turns. What should I do? Is there any way to get it out? Also, what size is the lower bolt to the housing? The one right by the wheel well, very bottom. Are there any tricks to removing?

Thanks.