Ohhh Chevy trucks from 73-91 are my specialty!
Well the main body of your model burb ran from 1973-1991. In the 70's the grill insert changed a couple times. in 78 The went from a exposed gas cap to a door. The door pannels also changed and they went to a spade fues box. In 81 was a MAJOR styling up date on the front sheet metal but doors from a 73 would still bolt right up to a 91.
Now there were some changed in how that third seat mounted. 81-91 I am not aware of any major changes to how that seat mounts. So the key is making sure you hae a 81 up seat. Where those seat mounts belong should be clearly visable in the floor stamping.
I just went and looked under my 88 that doesn't have 3rd seat but I was able to find a couple spots that look in the correct locations for the third row floor pockets. The rear set I was having trouble spotting. It apears they are over the fuel tank.
Here iare a couple excelent sites for GM trucks.
I moderate this one. Over 12,000 registered users. It's more 4x4 full size Blazer but plenty of folks that know the burbs as well. THe sites founder, Steve Fox< has a brother named Ken Fox that is very much the burb fanatic but doesn't post often. He hase several dating back to the 50's.
I go by Grim over there. Unless your a paying member you are restricted to "the Garage" forum. You will get any questions related to mount this seat answered in that forum. PM me if you need anything else.
Antother very good site is http://www.67-72chevytrucks.com
They have a 73 up forum that gets good traffic. A am again going by Grim there. Good traffic in the For Sale forums.
has a very active for sale section but I have warnings. That site is hard core. That is where the guys that make the magazines with their rigs parked upside down and on the cover hang and I don't mean the trucks with the bling bling these are rock crawlers running Rock well axles driving over things most people don't walk on.
It is tradition to haze newbies there. They do it to get rid of the wannabies and kids with dumb questions. If you want to learn how to make a four link suspension with 20 inches of travel running Airbags and hight adjustable with full hydro steering and setting ackerman angles to control squat......this is the place.
Should be fine posting questions in Forsale and proably Chevy but lurk for a while before making posts in General4x4 and Chit Chat. These folks have zero tolerence for basic questions. These folks are building comp buggies from scratch. The newbie 4x4 section is good for general questions.