Its all in the FAQ...
Ive done this upgrade on my ke20 and you just use the ke55 caliper to body hose. The connections are the same size between ke55, ke70 and ke20 AFAIK
Hey i don't know if this helps but my idle with the dellortos was all over the shop and it turns out ive got a an air leak where the #2 runner joins the head. So the motor was running mainly off the rear carby. Fixing the leak sorted the idle right out. Good luck mate.
I cleaned up a massive eagle one day coming along the bruce highway near the beerburrum exit. f@$k those things are big when your in a ke20. LOL. Luckily no damage only had to replace a headlight globe. The eagles fault though :y: Amazingly it just flew away.
I'm running a galant twin circuit master with stock ke20 brakes and it works a treat. The galant one has the same bore (i think) as the stock ke20 one but is twin circuit.
Just a thought mate, but a hilux diff could quite possibly be overkill for a worked 4k. I haven't managed to blow up a ke20 diff (smaller than the 55) with a worked 5k. Looks good so far. Keep up the good work :P