I learned long ago that when something is in question, like this, then it's always a good idea to bring your variables under control & Bert has it covered fairly well.
Pop the drums & have a look at the linings, if they are 'in service' items you can see how much of the surface has been in contact. If the contact is full length, then it's all good, move to the next step.
Check wheel cylinder operation. All good?

Then while the drum is off, ensure that the adjuster has full & free movement. In other words, ensure it will actually screw all the way in or out. If not, remove & fix.
Return adjustment to fully out position.
Disconnect handbrake at wheel cylinder.
Ensure that wheel cylinder slides along the slot in the backing plate. This is a single piston design & when the brake is applied, the piston pushes one shoe & the wheel cylinder is free to slide back & push on the other one, so make sure it's got freedom of movement.
Refit brake drum & wheel.
Adjust brake while moving wheel a little in both directions. This will help position the shoes correctly when the shoes finally touch the drum. Adjust carefully to ensure that all un-necessary slack is removed. Do both sides the same.

Loosen off handbrake adjuster & refit rod or cable then adjust handbrake. [ensure that the cable is free to move over the full range of movement]
Bleed brakes if necessary.

If everything is checked & found serviceable, then adjusted correctly, then it WILL work as advertised.
Road test in both forward & reverse & check adjustment again to pick up any settling into position that the brake shoes might still do.

Yep, that's what I have done several times in the past. It's a pain to do it all but my brakes always gave of their best & never gave me any grief once they had been properly serviced & adjusted.

it's all been said already about adjusting the rear brakes, but my little habit is to use a 1/4
inch drive socket to turn the adjusters. Put the side that goes onto the rachet onto the adjuster, pick the appropriate size allen key ( i usually use a 6 mm allen key & socket) & the risk of rounding off the adjuster is significantly reduced. The name for a shifting spanner around here is the nut f@cker. As the rear brakes aren't self adjusting, finding they're rounded off isn't fun. Later Nissans like the B310's & Stanza's had the star shaped wheel style rear brakes. they're a real pain to assemble compared to the 1200's. & they are supposed to self adjust by a linkage from the handbrake cable, but they never did.

Bert, Chris and Paul, thank you for your advice, every little suggestion came in useful and I am happy to say the little beastie stops like a real car should. I was actually quite surprised how much difference 4 corners stopping as versus only the front 2 makes, we went out on a quiet stretch of road yesterday and did some panic stops with only the front drums operational (these have been adjusted and bled from the start but I was ignorant on the back adjustments), then we put it back up on the stands and checked cleaned adjusted everything as advised and hey presto the darned thing stops u beaut.

In all the time I have been playing with cars I had no idea about radius grinding the shoes to the drums (although we did not need it in this instance) so a quick call to Kent Brake and Clutch (where we bought the M/C) brought me up to speed on that.

Chris your instructions took all the guesswork out of the equation, u dont write workshop manuals do you?

Paul, what a gem of a suggestion, still wondering how many more years it would have taken me to work that out on my own, scary thought.

Thanks again - John