Hey guys, I just fitted a water pump for an is200 onto my 2ng gen 1g-gte. It fitted without any modification at all, direct swap. It's a GMB one, so for anyone wanting a water pump in the future. Got it for $100 delivered from Goleby's Parts, they do a whole heap of 80's and 90's Toyota stuff, new and second hand. Here's their eBay page too:
Pretty happy with it all and hopefully someone else can use it to success too.