use whatever t-case is in the donor vehicle. or, if youd like, there are kits to bolt your factory t-case onto a fullsize transmission.
motor mounts are about the easiest part. you can buy mounts designed for the swap, or you can modify stock v6 mounts to fit.
certain transmissions can be bolted to your factory transmission crossmember. others require some modification to fit. wether or not you have to relocate the crossmember depends on what transmission you use. relocating the crossmember is as hard as drilling new holes and bolting it on.
your making this harder than it has to be. no, a v-8 swap isnt 100% bolt-in...but its not rocket science either. theres a ton of info on such swaps in the tech library and on the web. its been done over and over again and its very straightforward.
if you dont want to go through the "hassle" of swapping the engine, then turbo the 2.9. if you dont want to do that, change your gearing and drive it like it is. horsepower isnt cheap or easy...you have to work to get it. there are no bolt-on mods or bolt-in engine swaps that will give you noticeable improvements in power. if you dont want to do the work, leave it alone.
im sorry if i sound snappy. you just sound like you want everything, but dont want to do the work...and that just aint gonna happen.