Carpet isntalled with nails?

Ok, so I took some time and ripped out the carpet... Overall the condition is great. I got to it just in time, since some of the low spots were starting to rust... But I scrapped with a screw driver and it exposed the metal and no pitting that i saw.

The worst part was the house carpet that I pulled out was installed wiht nails... And the leaky tran and or engine from before I owned it, has everything lubed up. I believe the paint bubbling was from the oil and what not.

I am going to a 4 speed like the car was originally. Should be an easy swap sine the hard stuff is done.

Is the use of nails common? I would think not, but what do I know.