quick ? about late blazers
 

does anybody know what year they started putting the poly tanks in Blazers?

my bro has an '87, with a steel tank but he won't let me have it... so I guess I'm off to the boneyard, and I'd like to have an idea of how 'late' I can look through. also, if I need to move a crossmember do I move the rearmost one? (on SWB, z shaped with a hole for trailer lighting), and when I re-install it (if I even need to), do I need to use rivets? or will bolts do alright?

as always, any help would be greatly appreciated.

SEKE

I think the poly tanks are pure aftermarket. Far as I know all original tanks are steel.

yeah i think all factory tanks are steel my 90 is

my 90 K-5 Jimmy has a steel tank