When I went to a 8" rear end it was a complete (as they say) "drum to drum" swap. This was about 12 years ago and I think it was $116 out the door at Pick Your Part.
The 6-3/4" brake drums will NOT work. The center hole is different. As I recall there was possibly an issue with the parking brake cable too. Maybe someone else knows better. I just can't remember. I believe my rear end came out of a Mustang II. As far as the pads, mounts, U-bolts etc. go I the 8" tubes taper down and I believe the original 6-3/4" pieces mounted the 8". Again I'm not 100% on that but believe it is good.
The width is fine, no worries there. However, the centerline of the axle to the flange attachment of the driveshaft is different. I believe the difference is in the 1" to 1-1/2" range. So, the driveshaft is not the proper length. I was just very fortunate that I also went to a T-5, 5 speed and what was lost on one end was gained on the other.
As to ratios, the 8" Pinto rears came with 3.00, 3.40 and 3.55. There should be a tag bolted to the rear. Tire diameter and intended use/expectations plays a factor in what ratio is best.
Update: Actually as I (NOW) read through the previous post (should have done that before writing this post) I believe all these questions have been answered before. It would be beneficial to go back and re-read them.