It really all depends on what you want, a vintage racer feel would be to stick with the L-series. I love these engines, easy to work on, sound great and aesthetically look good in the engine bay. I also find them relatively good on fuel too!
Another reason why I will more than likely keep the L-series is that you won't get hassled or defected by the Police. If you pop the hood and it's a stock looking L-series I think you'll get less hassle myself. Even though I've been in an L-series still on twin SU's that produced 280HP and it was absolutely nuts!
You're not going to make gobs of power though without spending some time and money on it. It's definitely not an economical way to making power.
If you are interesting in building a serious L-series speak with Peter Mac on here, there are various threads showing the work he's done with them and power he's obtained but it won't come cheap.
If you like the idea of a turbo in a vintage car like the 240z then an SR20, RB or similar would be best. However if you want old school muscle feel a V8 would be awesome.
To be honest these cars are so light that you don't need massive power to make them go, I would like to see what a 13B or 20B turbo would be like in these, I know in my FD which is about 200KG heavier it feels very very quick, I imagine a single turbo 13B with say a GT35R making about 400-450HP would be absolutely insane and wouldn't cost a fortune.
The other advantage of the rotary is low weight to power ratio, you could stick that well behind the front wheels and have an almost MR drivetrain layout. However it depends on what you can live with . Rotary's do use a good bit of fuel.
Again it all comes down to your build direction, I love the old L-banger but it is dated now.
Perhaps ask for someone to take you for a spin in their car to get a feel for it? I know after being in a properly worked L-series powered Z I was like 'no need for engine swaps' .
thanks for advise.
i think the main problem i have is the fact that i have never driven/been in or even had to do much with L series engines, so im at a complete loss with how quick they actually are...
im wanting a fairly powerful car (ive grown up around 300zx's and old V8s) i dont expect it to be as quick as a 300zx z32, but i want it to be fun.
the rb 20 as i got it free would be good, if it comes under all the new rules that have come out (im pretty sure it does) and an engineering cert should stop it being defected.
im over v8's ive owned 3 old fords a 289 a 302 and a 351 and although they are a quick car, i dont think they suit the zed too well haha
ive driven rb20det (bog stock) and they are sort of quick in an r32 which are heavier, but in a 260 with just a few mods should be quick enough.
is an L28 turbo with just usually mods , eg cams, injectors, coolers and exaust etc enough to be able to keep up with the rbs?