Thanks for reply Tony.
 
It's NA so s54.
 
I spoke to my mechanic and he says he will send it away for a rebuild.
 
So a few thousand!!! eek!!
 
Oh well love the car so it must be done.
 
Thanks again,
Jem.

S54 ... I don’t know much about as only playing with e153 (turbo).
Few other members would be a better point of call for info.
The thousands is worst worst case scenario, on a lot lot wrong, depends on what needs doing. Best to expect the worst to get the best outcome :)

jemstar
Thanks for reply Tony.
 
It's NA so s54.
 
I spoke to my mechanic and he says he will send it away for a rebuild.
 
So a few thousand!!! eek!!
 
Oh well love the car so it must be done.
 
Thanks again,
Jem.

I’m similar to Tony in my knowledge of S54s but my understanding was they were a lot more common.

And as Tony said, really depends what’s wrong with it, if it’s some bearings and synchros won’t be as much as that.

Depending on your mechanic, the other thing is they really don’t want to spend time chasing a more complicated option that may work, but depending what they quote on the rebuild it MIGHT be worth trying to source an e153 out of a v6 Camry. I know 153s are very rare for MR2s and I think probably somewhat to find a manual Camry but given the sheer number of camrys out there and their long run (into 2000s) there might be good chance. I only saw one sell on gumtree yesterday for 600. I terms of what is required to get it to work on NA (i.e. shaft lengths etc) hopefully someone more knowledgeable will add some info

I believe S54 boxes are not that rare.
Maybe check out MR2 club of Australia Facebook groups.
I recoed my S54 about a year ago and found stuff like syncros, bearings, shims, circlips etc all available from Amayama.
Not sure about S54 shafts or gears, but to check availability you'd first need the part numbers.  

Jem when you say the gearbox has seized, what do you mean, what are the symptoms?

I have a good condition S54 I removed from my 1991 when I did my V6 conversion , always ran on redline MT90 and all gears change smooth
It is in WA but postage can be quite reasonable

Camry e153 internals fit in a mr2 e153. S54 being a different case, I dont imagine will work. The S54 is lighter and said to have better gearing for n/a engine.
To do the Camry e153, you need the e153 mr2 case and selector shaft (no longer available and I have tried many machinists to replicate and said no can do), preferably final drive, and oil pump.
To use the e153 Camry case, you need the front engine mount case component ($100), machining of the selector ($200+ depending on machinist) and the mr2 e153 items above being not available/cost too great.
Get the gearbox quoted by a professional, could be something’s small to something big... then make a decision.