I would like to highly recommend Race Radiators in Bennet St, Dandenong.
I've just installed my new 55mm 2 row aluminium radiator.
It was a custom one-off according to my design: 550mmx400mmx55mm core, downflow, with heater return, OEM radiator size turned so the overflow goes straight to the passenger side, OEM coolant level sensor (on the front side of the top tank, so its hidden under the cowl), and baffling in the top pipe to force coolant flow across the whole core.
I was charged $600 for it
, which is several hundred dollars less than the going rate. They also do rads in 40mm core, which is meant to perform brilliantly also, for cheaper.
RR use PWR cores, which are some of the best, most reliable cores available, and their workmanship is excellent. All welds were clean, and the tanks were nicely cleaned up and rounded off before being britexed to give them a nice clean finish. Polishing would be extra but I did this myself on the buffing wheel. Really, the work was excellent and the price difference of the competitors does not really equate to a better product IMO.
The radiator is also warrantied so long as you do the proper maintenance for aluminium rads (stray current test and use the correct grade of coolant).
RR do lots of work on rotaries - eg for IPRA (they do some work for Xtreme Rotaries, such as on Rohan's old IPRA racecar), and they mainly do streetrods, V8s and other circuit cars.
My only criticism was the turn around time, which was 2 weeks, but the recent floods in SE melbourne had wiped out all but one welder, so it was not really the workshops fault IMO. They were also extremely busy with Summernats coming up.
Cooling is now unbelievably good.
I'll put some pics up as soon as I can get them hosted.