Ran Mac longtubes on my 4.0 (they're currently for sale). No major issues; had custom downpipes/connecting pipes made for them instead of using a prochamber or such.
Putting headers in a 4.0 is a helluva lot easier than in a v8!
They did, Ron (navbtcret) ran the stainless works ones, he said the fit, build quality and finish were exceptional. Tony (ranebowcyxx) had the Mac's with his procharger, fit wasn't perfect and they had to be worked a bit to get in there just right. Same with pacesetters, requires a little bit of work to get them to fit right.
Stainless works are great as well, but pricey. unless someone has a used set...I thought Stainless Works developed long tubes for the 4.0 too, might want to call them direct and ask if you are interested.