between what years are the best matches for a 78 whats compatiable with it so when i go to the pick n pull i know what years i can snag stuff off i havent really been able to find a anwser for that

 

i know sheet metal for repair panels will be 73-91. i'd say the closer you can get to the 78 the better. also alot of the chevy trucks the k10 and others crossed parts too. found this on lmc that shows what they changed each year.

http://www.lmctruck.com/icatalog/bzc/full.aspx?Page=10

 

73-80, pretty much everything interchanges. I believe that in 81 they changed a number of things in terms of dash components, etc.

It all depends on what you are looking for.

 

73-79 everything foward of the front doors on any full size truck will match stock.
80-91 blazer and suburban they changed the body lines and grille slightly along with a change in the radiator support.
other than that most of the mechanicals are easily swapped and with a lil homework all parts are swappable. 73-91 blazers , suburbans ,and heavy duty trucks
73-88?--1/2 ton pickups all share parts .

 

A decent way to determine what interchanges is to browse through a few of the aftermarket restoration supplier catalogs looking for A) what you need and B) the year ranges that include your truck.