Any complications with swapping the later fb detached pick up tank to a 82 fb?

What will I need to change? The sender is still located on the left rear wheel well

 

All 81-85 tanks are the same size and shape so it will bolt right in. Everything should just hook up the same way.

 

Sorry to disagree, but that is not true. The 84-85 tanks are a different shape than the 81-83 tanks. The top section is wider on the 81-83 tanks and the 84-85 tanks are a little taller.. The car body is also different. The hatch floor between the left inside wheel well and the spare tire hole is about an inch wider in 81-83 than 84-85. We went through this several years ago. If you look closely at the 83 and 84 tank pictures on my website you can see that the top section is a slightly different size.
http://intertron.com/ron/tank.html

Here's a thread where we talked about it.
https://www.rx7club.com/1st-generation-specific-1979-1985-18/gas-tank-628743/

Might be able to make a later model work, but not a direct bolt in. Earlier model will definitely not fit in 84-85 without modifying the body or the tank. Several of us have tried.

 

Yep I'll bet you'd get real frustrated trying to install a late tank to an early or vice versa. Besides the size differences that 74RX4 points out, I seem to recall reading somewhere they have different volumes and the sender units and plumbing are very different, as you can see from these photos. The 84/85 tank is on top, the 83 tank below





In fact I now have two tanks because I just picked up an 85 GS that didn't have a tank and although I already had the 83 tank shown above, I didn't want to mess with trying to install it in the 85 GS.

Fortunately Rotary Buddy Alex had just dropped the tank from his 85 FB race car to put in a fuel cell and he offered his 85 tank for the 85 GS project (the upper one in the pics). So kudos to Alex and I suppose karma dictates that I now find an earlier FB in need of a tank and donate the 83 tank, which originally came from Chris' white 83 GSL called Sexy Pants.

 

I just put the early style tank in my 85 this spring it was tough to get the drivers side strap on but once I had a few threads started the impact took care of the rest. It doesn't seem to have crushed anything I also used the old style 2 pin fuel sending unit with the three pin plug in on my car and my fuel gauge actually works!!!

 

Sorry for the misinformation guys, I assumed that since they had the same capacity they were same. Weird that Mazda bothered changing the body like that. Good to know!

 

I installed an 84-85 tank in my 81. It seemed taller so I used some longer strap bolts. Worked ok.

 

Here are some pictures of the left side of the hatch floor showing the difference between a 83 GSL and a 84 GSLSE. I think the shape and/or location of the spare tire well is little different also. All the 84 and 85 cars I have (each model) measure the same. Can anyone attach pictures of 81 and 82?

 

If I get a chance to toinght I can take pics of my 83