From that same diagram, the position of the hooks on the main springs appear to indicate they should be on the inboard side of (behind) the brake shoes. That would alter the pull on them toward the backing plate.

Rear shoes have a Center Spring Clip that work for exactly that = Holding the shoes flush to the back plate

Perhaps you need just those 'Spring clips"

item 25 in the Diagram


https://mossmotors.com/mg-midget-austin-healey-sprite/brakes/early-948-rear-brakes

Moss motors, google search, 1965 Austin Healy Sprite Moss Motors rear brake shoes, there are alot of pics there, our host also sell's these parts, i'm sure they would have pics too
 

While I have worked on Spridget brakes... it has been too long and I don't have pictures.  

I suggest you visit The British Car Forum and post your question in the Spridget section.  You'll get a lot of Spridget specific eyes on your question there.  Membership is free.

//www.britishcarforum.com/bcf/forum.php

Hello,

I am having a problems with the back brakes on my '65 Sprite. The person that I bought it from didn't really know much about these things and did some rather strange things to it under the guise of keeping it running. The brake shoes are a perfict example. The springs were on upside down and were rubbing on the axle. When I started restoring the rear suspension and tried to put the new pads and spring on correctly I found out why he did that. If I put them on correctly the pads pull away from the backing plate. This can't be correct, is it? I must be doing something wrong. All of the diagrams that I have are exploded views. Does anyone have, or know of, a picture or diagram of the rear brakes fully assembled?

Please help.

I didn't find the right solution from the Internet.

References:-
//www.spritespot.com/phpBB3/viewtopic.php?f=4&t=396
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Thanks