My DL LTD is hard to start, i changed battery ald also charged it. Starter motor turns over very slowly or not at all. I've changed starter motor as well. Tonite after changing oil the red charge light was on. Checking the alternator, i discovered a plug on the regulator plug corroded and broken away. Maybe this has been causing the loss of power?

One way to find out..

I reckon that would have a crap load to do with it.

Fixed the connection, no different to problem! Engine still sluggish on take-off and acceleration.

i found the same thing with my old ef xr8, when it was warm to hot it would be a pain in the a** to start. i got a relay put in for the starter motor but it didnt make too much difference tho. changed the battery aswell

Drove the LTD to town today (30mins in the heat), parked it and went to start it straight away and it barely turned over! Managed to fire it up and go to a mechanic i know. Alternator seems to charge battery ok, battery was load tested ok. Starter didn't seem to receive full power from battery. We used an alternative battery to engine earth lead but this made little difference to starter cranking speed.
The starter was replaced earlier and different batteries used. Not sure what else to do...maybe the alternator is faulty or the regulator or diodes? The alternator has been replaced at some stage. The starter only cranks slow after a long drive, when lights/indicators etc are used for a period of time. Seems ok after short trips.
I'm lost to what else to try to fix this stressing problem. I don't want to continue carrying a spare battery in the boot for ever!

bad earth somewhere? battery/block/starter motor?

I had this same kind of problem in the past with my AU fairlane V8. - a very sluggish starting. I went to ford and they replaced my battery but the problem persisted. I then went to local mechanics, midas almost averywhere and no one could resolve the problem. Until one day i got stuck in Westfield car park. I called NRMA and when he arrived, he fixed in in less than 5minutes. It was a loose connection on the wire leading to the starter motor.

How's the timing on it?
Has it been set properly?
I dont know if you have to jump some pins under the bonnet or not,
but if so jump them and reset the base timing maybe also rest the ecu at the same time.