Morris Minor Owners Club

what diff is easiest put into the back of a 4 door saloon?

Any diff fits easily ! I think it should be 4.22 ratio if 1098 engine.

a 4 door saloon?

what car is it? (ie what year)
From 53 onwards the diff footprint is the same (I'm not sure about the MM axle pre53). However in 62 (when 1098 was introduced) the filler position moved between axle and casing.
There are many many available options including
5.3:1 (early minor - cant remember which ones are which)
4.55:1 (948 Minor)
4.22:1 (1098 minor)
3.9:1 (not standard Minor - Riley 1.5?)
3.7:1 (not standard Minor - MG 1275?)

Therefore if you mix up the combinations you can get two fillers or no fillers.

Therefore best option is to use the diff that is correct for your car, but if you want a 4.22 diff on pre 62 car it is best to use the complete axle.

I bought two minors and one was registered and the other had lost its id. the first minor was a 1961 reg the second one had its engine number and a number on the body on the top left hand side of the body. is there any way of knowing the cars spec from these two numbers?

which one was the 5.3:1? I thought my sidevalve is 4,22:1?

Nope. Have a look at: http://potteries.mmoc.org.uk/Identify.htm

Under gearbox /axle info

I meant 4,55:1

When did they use the other two? For exceptionally hilly area's?

Options, so perhaps so.