The 80 has not been started yet over at Proffitts. He is very busy. After he finishes Exiled's FJ62, Jeremiah has 10 more to do. Yep, you heard me, 10 more 4BT conversions to do.
He has 3 FJ60's, 3 FJ62's, 2 FJ80's, an FJ55, and FJ43. It will be like an assembly line of 4BT conversions.
I agree with lovetoski, the answer will come from within. I personally would go with a 60 series. Sometimes I wish I had gone with a 62 for the power windows and locks. But, I am completely happy with my 60.
I have clocked almost 10K miles in 5 months of driving it. I always calculate my mileage when I fill up. I have gotten as low as 23mpg and as good as 28.5mpg. The 23mpg was pulling a heavy trailer over a mountain pass. I average 26/27 on most fill ups.
So, I would not lose too much sleep over wether you want to do a 60 series or an 80 series. I think the 80 would be cool but obviously more expensive. The lift kits are more expensive, hell everything is more expensive.
Where do you live that 60's are $4K? Where I am, they come up for sale a lot. People are dumping them left and right because they can't afford to drive them. I bought mine for $1K and it's really clean.
BTW, I have a 1989 62 for sale, pictured below. Would be perfect for a Cummins conversion. I bought it just for the hell of it but, I do not want it anymore. It has 272K miles on the 3FE. It needs a fuel pump to run but just rip that motor out, and put in that 4BT and your golden. Asking $1,000.
And, it's already over at Proffitt's begging to be dieselized. I can hear it now, Cummins, Cummins, where art thou Cummins?