"the classic "master cylinder pump" pedal". 
Those symptoms indicate master cylinder could be leaking internally.
 
Delete ABS: You could simply get new pipes made up to bypass it, however before you do that first investigate the master cylinder. 
The brake proportioning valve is located in the pipes between the M/C and the ABS unit.
Obviously, if you make up new pipes to bypass the ABS, you will also need to plumb in the
prop valve.
The pic attached shows a 1" M/C, 94+ booster with prop valve on a car with ABS.
 
 
 

 Thanks Guys,
ok I'll go back to my original plan which was to reco the m/c?
Some risk is that the cylinder is bad and new seals may not solve, or wear out quickly.
 
Another q, I see repeated mention of significant improvement later Sdubs had using a different, thinner booster.
Is that something that a 1990 m/c can bolt straight onto ? Or would I need the later model mc/ and callipers.
Until I have reco'd the 1990 m/c I don't know if the brakes will be adequate or not.
 
Another q, I read that the early brakes will fade on the track after a few laps, hence the changes made by Toyota.
I don't know much about that , is it a hydraulic "boiling" or the pad/disk grip issue ?
Does it come on suddenly/dangerously or is it something that progressively worsens ? 
 
 cheers

"Another q, I see repeated mention of significant improvement later Sdubs had using a different, thinner booster.
Is that something that a 1990 m/c can bolt straight onto ? Or would I need the later model mc/ and callipers.
Until I have reco'd the 1990 m/c I don't know if the brakes will be adequate or not."
 
Re - read my post on page two of this thread!!

 Thanks Redd, it seems there are some options available and appreciate the checkvalve comments
 From 5sgte's post immed after yours on P2, he says he bolted the orig fat booster to the later 1" m/c, so that would imply the reverse , a post 94 booster would bolt to the orig 7/8" m/c.  Not saying that's what I'll do, but it seems to indicate that versions will at least bolt together.
 Anyway just ordered the m/c reco kit from USA, then after payment had this anxious thought, "I hope
the m/c is original and not  been upgraded by a previous owner !!??"     Doubt it....
 
cheers, undoubtedly more questions will follow...

TwoDogs
Another q, I see repeated mention of significant improvement later Sdubs had using a different, thinner booster.
Is that something that a 1990 m/c can bolt straight onto ? Or would I need the later model mc/ and callipers.
Until I have reco'd the 1990 m/c I don't know if the brakes will be adequate or not.
 
Another q, I read that the early brakes will fade on the track after a few laps, hence the changes made by Toyota.
I don't know much about that , is it a hydraulic "boiling" or the pad/disk grip issue ?
Does it come on suddenly/dangerously or is it something that progressively worsens ? 
 
 cheers

There is numerous factors that impact brake performance. 

Brake rotor design and material, pad material, brake fluid, brake cooling and overall size of the components. 

I have tracked the early brakes, they fade over time - It's very progressive and gives you plenty of warning that you need to do some cool down laps. If the car is NA or a stock turbo, you can most likely get away with a good set of rotors such as DBA T3's, a good set of track/street pads and some high temp brake fluid. 

I have upgraded to the DeltaV brake kit, with T3 rotors, race pads and brake ducting. I have never experienced fade with this kit, however it may be surplus to your requirements.

Thanks Eric, nice description.
It encourages me to leave it all stock (but working better than currently) and then upgrade if necessary.
 
Any reason why I shouldn't mate one of the powerful boosters to a 90 7/8" m/c ??
 

I personally liked the firm pedal that the early model provided. All it will do is decrease the force on the pedal required to brake. 

If I was in your position, I would leave it as is and install some high quality track/street pads with high temp brake fluid. If you feel it needs more assist later, then you could add the other booster.

Yep that seems like the plan. 
I look forward to having the pedal firm.
TBH I can't recall the pads I put in.
 

This morning, the only place in the US that did not list the reco kit as Discontinued, sent me an email
to say they can't fulfill the order. So looks like I will be fitting an m/c from a different car.
Currently 1990 7/8" ABS - any suggestions ?
Is there a 15/16" m/c with will bolt straight on with similar exit holes for the piping?
and is not so old that reco kits are discontinued ??  :o)
cheers,
 

They're interchangeable, just need to keep abs with abs, non abs with non abs to suit the hardlines.