early/late tank differences
 

I was looking to sell my left & right tanks off my '74 C20 to a buddy who has an '87, but looking at LMC and Classic catalogs, there are different stocking #s for 73-80, 81-86, and 87-91. I figured that 87-91 being injected could have a different setup, but what would be the difference between 73/80 & 81-86?

Re: early/late tank differences
 

Yes 87 has. Baffles inside the tank... It's the only difference

Re: early/late tank differences
 

The hose fittings were different diameters between my 78 and 85 tanks. The 78 was set up with the old style leaded fuel filler necks and the tanks had larger fittings.

Re: early/late tank differences
 

The opening size of the filler hole is different on the 73-81 vs. the 82-91

Re: early/late tank differences
 

So I could use these tanks on a later truck if I used "period correct" filler necks/hoses? Would an early filler neck both right up to the later bedside?

Re: early/late tank differences
 

Piecing together fuel fillers can be a real chore. Parts are hard to find and expensive when you do. When I was building my 78 stepside, I tried to use a freebie 87 model tank. After a bunch of effort to figure out a filler setup due to the different size hoses, I found it cheaper to just buy a new tank of the right vintage. It was under 100 bucks delivered.

Re: early/late tank differences
 

Realistically the answer is no as TX_Firefighter said.
The tanks require the associated parts. The filler neck on the early versions mount differently to the bed.
If the filers were from a truck with gas doors they would work. If the filler mounted to the bed with a cap they won't. (Barring modifying them)

Re: early/late tank differences
 

The early tanks had a smaller inlet on the tank. I know because I acquired one for my 83 build and it wouldn't work. It's still sitting in my garage at home!