Hey Kevin, about your question on 281ranger's fuel tank. Like he said thats a factory rear auxiliary tank. I installed one in my truck also (I have a '92 Ranger). Unfortunately they DO NOT make these tanks new, nor do they make the sending units new. You have to find original parts, which can be very tricky. I was lucky enough to find one from a member on here by posting a wanted ad in the "wanted to buy" forum, it came out of his daily driver, he didn't use it so he just took it out and sold it to me, I had to get the crossmember seperately (also very hard to find). Another problem is I'll have to modify the sending unit, it has the wrong ohms and doesn't work properly with the newer gauges.
All in all, get a fuel cell, LOL. OR, you can use a Bronco II tank, its 22 gallons compared to the aux tank's 13 gallons. You can get them and the sending units new. You just need to install the crossmembers from a Bronco II. You have to cut the inside of the bed to fit it, but I have a feeling you'll be doing that anyway.
The IRS should be cool. My friend is putting a Mark VIII IRS in his '98 Ranger. Its bagged and it already has a stock floor body drop, he built a new frame out of 2x3 from the firewall back, now hes just adding the IRS. He had to narrow it 6 inches overall, which he did by fabricating new control arms.
Heres a picture..sorry for the quality its the best I have lol.