The way I am LS swapping I will be about 150lbs over a BP. Engine is ~100lb heavier give or take(dressed BP is ~300, dressed aluminum LS is ~400). BP motor is iron block/aluminum head vs. full aluminum LS. Trans is about 40lbs heavier(90lb Miata 6spd, 130lb T56 Magnum F). Rear end is +10 give or take(55lb miata vs. 65lb ford aluminum 8.8). Sub frames are heavier than factory pieces(unsure by what). Driveshaft slightly heavier. Axle shafts slightly heavier. Front to rear balance changes towards the front a bit. A buddy runs a 50lb steel plate in his trunk to balance out the car a bit. With 400+ whp it simply doesnt matter near as much if you add 150-200lbs onto a 2200lb car. Its going to be a violent ride regardless.
Rotary's have shit support in general and make what, 50hp over a BP at a bajilioin dollars cost. Would be a cool project, but just no... My buddies dad has one. Its fun, but he takes out his other cars far more often.
k24 swap costs damn near what an LS swap costs to do correctly and you end up with half the HP and a motor that vibrates itself to death, still dealing with the shit Miata transmission and rear end(unless you swap to a different trans and rear end, which just adds more cost)... I think they can make fine conversions on the street, but put them on the track and you are going to blow shit up.
Ozarks isnt nearly as bad as it seems IMO. Even the first time I went I was like "this isnt as bad as people make it out to be". MOST of the "haters" of Ozark that tell you how dangerous it is have never been... but thats the case with almost everything these days when somebody tells you how to do something and you say "how many times have you done it that way" and the answer is "well ive heard" or "I watched it on youtube" or "ive been elsewhere so that corelates to this also"... the answer is they have never been somewhere or done something that they want to give their opinion or expert advice on. None of my track buddies will tell you Ozark is dangerous. Does it require a bit more skill than other tracks, sure, but dangerous...no. Its an FIA rated track so its got runoff, armco, tire walls, sand traps, etc... where they need to be.
Dont know on the NC although we are building my buddies after we do mine. On an NB you gain about 100lbs up front.
As I laid out above its at least 150lbs and probably more like 200lbs. But going from 130whp to likely 400+ whp, 200lbs isnt going to affect anything that I will be able to tell. Likely about +100 on the front end. My BP is pretty stripped and so will the LS. No A/C, no Power steering, etc... Just an alternator, water pump, etc... LS accessories are far heavier than same on a BP so I expect to be under that 100lb weight difference by a bit(maybe 10lbs). I have no way to weight the motors unless I can get a friends 1000lb corner weight scale.
Here is an acquaintance LS Miata. He's been doing LS miata stuff for like 6 or 7 years. Has it pretty dialed in. 150mph in a Miata is NUTS...