Well my 73 Fury has the same style rear quarters and I have a 285 40rz r18 in the rear, I had to run a 5/16 spacer to comfortably clear the rear leaf springs, only because I got the rims second hand and the offset wasn’t quite right though. My question though is does any body know what the stock wheel offset and back spacing is? I can’t find it and I’m looking at a set of 15x7 cragars and I need to know if they’ll fit because I have to use a 1 inch spacer up front to clear my tie rods with the 18x10 rims

 

I put the stock road wheels on my 72 fury 3 and just put 255/70/15's on the back last weekend it was hard to put them on. The clearance between the inner quarter and drum would not let me put the tire "up" in there so I had to put air in the shocks and raise the car way up and set the bottom in first. That allowed me to put the wheel on. I hope I don't ever have to change it on the side of the road. But once on there is plenty of clearance and looks great. I have 235/70/15's on the front.

 

Yep. Situation normal at my house. You need enough jack to make the suspension sag. That's why they came with bumper jacks. Even with stock tires if you lift from the axle like you would do on a heavy truck, you just stuff the tire up in the fender well.
I keep a floor jack ratcheted down in the trunk of the 300. The factory jack is just there to hold the spare in place.