It turns out that the thermostat housing from a 1967 - 1981 Toyota Corolla is the right shape and dimensions to fit onto a Bellett G151 engine.

A 52mm thermostat also seems to be the best size.

I'll post some pics to confirm this after I driven the car for a week or so!

Cheers,
Ross

OK, here's the follow up for the thermostat housing. As you can see from the first photo they are not a 100% match but the bolt pattern is identical and the angle of the outlet is right.



The next pic shows that the oulet's angle is again slightly wrong but in this case beggars really can't be choosers!



And lastly, the finished product. I had to use two gaskets when I put this back together but this was mainly because I was worried about breaking a second one plus the block wasn't particularly flat!

As you can see the outlet pipe is noticeably bending the top pipe but I don't think this will effect anything



I'll post again once I can actually drive the car (the brakes are stuffed again!) and have had a chance to see if it leaks etc.

Cheers,
Ross

Looks like it'll do the job. You could probably cut about 2cm off the radiator end of the pipe and get it fitting straighter, though.

WTF has gone wrong with the brakes! they worked killer when I drove it!

The back right wheel cylinder failed in a big way... Went out to move the car to do the thermostat last week and it wouldn't move... On closer inspection the back right wheel was sitting in a puddle of brake fluid (the entire reservoir to be exact!).

Pulled it all apart and cleaned it all up but might need to get the slave cylinder recon'd before I can get it on the road. I'll find out tomorrow!

what a pain in the arse!

Reference to thermostat housings - Not too many years back, I was able to buy the Genuine part from ADELAIDE TRUCK SPARES. Evidently the same part is used on a small Isuzu truck - model unknown.
The label reads
ISUZU GENUINE PART ;
ISUZU Pt No. 9-13713064-1;
P No. 94021888;
Des PIPE;WATER
Fig key No. 031-049

However, putting all that aside, I am currently running a WO33 from Killkenny Castings which is to suit an RT18 four cylinder engine from a Toyota 1977 RA28 Celica. A housing from an RT18 engine in a Corona does suit but pipe exit is at slightly different angles I believe.