can anyone tell me if a mx5 gearbox will stand 200 bhp please or would a rx8 gearbox be a better option ,

My hairdressers currently shows 161 RWP so into the area you're asking about.
Others have gone a lot higher with the standard box.
Mine has done 20k miles in my ownership and the previous owner drifted it - so far no probs but choose your box oil carefully they're not all the same..

Other consideration is that there are a lot more MX5/Eunos around than RX8's so if you do lunch one replacement easier/cheaper.
Also if you're putting it into a kit then the reduced weight will be kinder to the whole transmission train.
HTH.
Cheers, Pewe10

I ran 225bhp on my 5 speed for a while then upgraded to 6 speed.

I think 250bhp/ 200ftlb is about the reliable limit when used with a turbo engine for the 5 spd 300 ish for the 6

I gave away 2 good 5 spd boxes as they don't seem to have any value. So if it does break you won't be spending much to replace it! I can't see you having to spend more than £50

Which generation box are you talking about?

The mk1 and mk2 box routinely take 200bhp in an mx5. In a much lighter car it will be fine.

The mk3 NC boxes are considered a little stronger again. They are routinely bolted up to high power duratecs and now the ecoboosts and I've not heard of any failures. I'm pretty sure the NC boxes have the same internals as the rx8 box too.

[Edited on 15/11/16 by sdh2903]

Thanks for all you're advice I think i will go for a mk3 box I don't supose the propshaft is the same spline as the type nine by any chance