(BMW 3 series) OEM seats drop right in.
 

So I got tired of sitting on the NOT so comfortable factory seats. I was browsing CL a while back and stubbled across come 3 series all manual tan leather bucket seats. Although I did not install them right away I was pleasantly surprised that they dropped in with very minimal amount of work and $. As you can see from the pictures. The front inside rail mounting holes line the seats up perfectly centered with the steering wheel, so that is where I started. I bought 2 pieces of 1/4" x 2" flat bar and 1 piece of 3/8" x 2" flat bar per seat. The total for the steel was no more than $25.

Luxury!!! Looks like you got them well secured. One thing I have noticed about Volvos (and Saabs) is that they use some serious seat fastening hardware.

Also liking the 11-ball shifter knob.