Well, for the transmission oil cooler I'd just order from Summit Racing or Jegs... you can probably get them for a decent price locally at a parts store too. You will have to extend the oil cooler lines and run them up to the new cooler.
Protect the hoses: Take some larger hose, slit it lengthwise, wrap it around the oil cooler hose and zip tie it in place anywhere that the hos might rub a rough edge.
The new cooler can be attached with
these to the front side of the radiator, A/C condenser or the back side of the intercooler (if applicable). The coolers come in many sizes wo measure first and be sure of what size you need; if there is any doubt get one a little smaller.
I've been running a Koyo 1JZ rad for about 5 years now... never had a problem myself. Since it is for a 1JZ there is an extra threaded hole at the bottom (right next to the drain) which needs a plug (a radiator plug from a Subaru fit perfectly for me; don't remember what year and model it was from though). You also need cut a small piece of aluminum and bend it into a loose Z shape to firmly clamp the bottom of the fan cown on the left side. AND you need to trim the rubber bumpers which sit between the radiator and the frame down around an 1/8" or 1/4".
The transmission cooler is the hardest part, IMO. It only takes a couple minutes to get the radiator modded and mounted.
I bought my radiator on e-bay... I think it was just a hair over $300. The transmission oil coolers can be found for as little as $25. If you're up to the work, you can upgrade the system for less than a factory radiator costs. Don't forget there will be the expense and labor of making extension hoses.