They're VERY comfy! Can be a little hard to get in & out of if you're over 6' or 220+ lbs. These are the Procar "Rally". The Elite is a little wider with smaller bolsters, and might fit larger frames better. I'm 5'9" 180lbs, so it's not an issue.
Shop around - I bought mine from Summit. Delivered price for seats, frames, & freight was under $700. Most of the Mustang parts houses are $700 + freight...
So are the only thing you need to mount them are the adapters that you buy? i've been checking out summit racing and that seems to be the cheapest way to go.