Imagery,
It's your truck and your money, so if you really want to go the J spring route, then certainly go ahead. Just a few things to keep in mind. There is no one that knows more about the 80 suspension, in the states than Christo and his crew. .... and I should say elsewhere, but I'll stick with here.
Most guys running J springs are taking their trucks through really sick terrain. That said, even the stock suspension and normal 2-1/2" OME lift on these is amazing. During a recent outing, I spotted an 80 with stock suspension and trailer hitch, with 33" TrXus, through what other guys were getting winched out even though they had 35's. Some times more time behind the wheel is the best solution.
Christo is, as always, giving super advice. You need to understand this is a comprimize. You can not expect to lift a truck up to 5", run 37's, go 0-60 in 4.5 sec, get 40 mpg and maintain all the stock handling. Something has to give and your wallet isn't always going to be able to make up for that. Once you hit 35's, EVERYTHING changes. It's a gradual effect, but seems to gain momentum at 35's. That's one reason why I run 295's on street and keep the trail tires for just that - trail.
You're talking going up high. Other things to consider are your cornering and how you do in offcamber situations. Do you like the smell of urine on the floor? Well, get some more lift and get off camber, and you may have some.
Seriously, everyone is trying to give you good advice. It's your money and your truck. IF this is what you want to do, then do it, but.... most of us would not given your situation.
