aaaahhhh I topic I am so in tune with bro!
first of all.....I have experience in all said cars henceforth that I pseak of and I have spent the majority of my childhood hotrodding imports........thats all dad would get unless it was a TRUE american classic.
Ok so here we go.....
concerning the Nissan 240......find a S13 chassis model...I believe these to be previous of you indicated model years...they had the pop up headlights and make sure you choose a notchback version........frame rigidty will help you immensely in the track ideas I believe you to have...whether strip or autocross or both....this will be a huge help. Also the S13 cars came with drivetrains built to handle upto 400 HP (they are called Nissan Silva's in the japan and the 240sx is a direct dissendent of the silvia bloodline...a couple more bucks in the drivetrain will net you the ability to go 800 ponies real cheap with some shopping for the right parts...name brands arent your friend here. if you choose the silvia/240 bloodline........have a sr20DET (important it has the DET on the end and a red valve cover is desirabe here.....this is a 400 ponie turbo motor that literally bolts right in and all you have to do is re-route 2 heater hoses and lengthen a cable with some splicing......all very easy to do and can be accomplished in a weekend without any hard work...can be done in a day if thought out properly and I have the website to show you the way and the jig to even set it up and install cleanly to the point nobody will know whats in there............till you rip em a new ass!!
the RX-7 is a great car (ala fast and furious) but if you see a check engine light on..............walk away.......means the motor is history and will need a imminent rebuild.......the rotors have a small ass seal that once it rots out (and they will no matter what) the only and I mean only fix is a rebuild....that seal being crapped out means things have gotten into where they werent designed to be.....oil, cooling fluids...etc. keep a SHARP eye on these factors when looking into these cars
The Honda has a great following but if your looking for real HP....plan on building the bottom end as they just cannot handle boost very well........heck they are engineered within mills of their life to get where they are......are they tough cars and yea they have the following to back it and the aftermarket even more so...........but if you plan on getting in on say a turbo.........plan a new engine along with it.....now they have fully gussetted motor blocks that can handle all kinds of power.............IE:Spoon engines and such.............these have bracings and such where the factory left off due to :
#3 mandations that wouldnt allow for it
money wise you are looking at close to the same for planned upgrades I assume you would look into.....turbo, nitrous, timer and engine management...all gonna be close in cost...some harder to install but overall look and cleanliness will be a tad better....or save a buck and maybe have to fab a touch yourself.
Greddy and Turbonetics make GREAT products for any one of these vehicles and nearly all of them are intertwinable to each other so you buy a greddy exhaust and a turbonetics turbo........they will still work with each other.....NX (Nitrous Express) is the proven capable player in the import market for the simple fact they follow the K.I.S.S. method (keep i.t s.imple s.tupid) nothing fancy.......proven and almost 100% reliabilty has brough them from nothing to a major player in this segment
another to look at is the 88-91 honda civics......yea they come stock with a shitty 1.5 liter motor....but the b16a first series (non OBD) motor will almost totally bolt right in........thats 175HP stock from a 4 banger.....again for serious HP you will need to build the bottom end but it aint hard to do.
anything more yo need to ask or have question on...................ask away....i am 100% comfortable with these issues.
Hope that helps a little bit
good luck on the hunt...and ya never know....get one of those babies and I may JUST show up on a doorstep with tools in hand.....I freaking LOVE hot roding imports