I ran the stock H145 with my A15 for years with no problem. I even ran it with a 50hp shot of Nitrous with no concerns. I replaced it with a H150 when the motor was supercharged. The spider gears on the H150 were welded up to lock the rearend. The H150 didn't last very long.
I am now running a locked H165 which seems to be bomb proof. I see no reason to go any larger than the H165.

i like my gearbox in one piece too much to do that!! i only have one 5 speed to play with

It'll last normal driving, the only time I broke a H145 was when I popped the clutch with the car rolling, turning right.
It broke a tooth off a spider gear because the tyre gripped, instead of spinning. I also used to drag race a 1200 sedan with a worked A14, 245 wides slicks in a sticky compound & an open H145. Never a problem. If I'd welded the diff centre,
however, the axles would have broken the first time I popped the clutch. H145 or H150 doesn't matter, it'll last with a normal driving style,particular in a light car like a 1200 or a Morrie. With the H150 centre into a H145 housing, a 2 mm thick spacer has to be fitted between the centre & the housing, or the axles won't line up properly. I'd only do this if you wore out the H145 & couldn't find another one & your only alternative was a Sunny or 120Y diff centre. All it has to be is the same shape as the gasket & 2 mm thick.

If your not intentionally doing things to try and kill it it will be fine, it will cope with spirited driving but not repeatedly dropping the clutch at 6000rpm.

Should be OK, I only stuffed mine up by doing burnouts, and I had an A15 etc.

ooo thanks, its a h145 no doubt.

now that we have cleared that up, will it handle the jandal or should i expect it to die a quick death? its not doing burnouts but will occasionally see open throttles, where my fuel allowance allows lol

I had an H145 behind a big HP bored out A15 for many years without incident, if you drive like you say you will never have a problem.

You put the spacer with gasket either side between centre and the housing.

H150 should have a larger rectangular tailshaft flange (left). H145 has butterfly shaped one (right).

well i am presuming that is a 120y diff, the engine that came with the car was out of a 120y. How can i identify that this would be a h150 or not? if it is infact a h145 and i was to put an h150 into it, where does the spacer you speak of fit in to the assembly? thanks

If its a 120y diff it should be a h150 witch should deel with a standardish a15 fairly well

But if it is a h145 you can put the sunny center into the housing wit a 2mm spacer.