Personally I reckon you'd be crazy doing an anal resto on a HJ 253 Sandman. It'll cost you 3+ x what the car would be worth finished! For a HT-HO or a GTS327 or A9X it is understandable, but for a far less valuable vehicle just restoring it to be useable is the go in my opinion. The whole date code, NOS numbers matching BS belongs in the muscle car arena, not the Sandman/GTR/SLR realm! If the car is a proper survivor though it is worth trying to make it right, but once it is painted close enough is good enough in my eyes!

On the water pump issue, the best ones I have found are the later pumps to suit mid VB onwards (up to VSIII in late 2000). These have a longer bearing and have a sandwich plate at the back of the pump. The pump is longer so you need a shallower pulley and need to shorten the fan spacer by about 20mm or so. When I put one of these pumps on my old Overlander 308 all overheating issues dissapeared. It had one of the awful fan type impellers on it, the later pumps have a cast barrel style impeller. I am sure GMH still sell them new in boxes, they'll be an aftermarket part though. Super Cheap even sell them.