If you have an OHV just run the first gen box with the stock first gen lines. If you have an SOHC you can do what I did and run the first gen box and for the return line you just have to find a barb that will thread into the return port on the box and run some line thats rated for ATF/power steering fluid from that up to the reservois. Add in a cooler if your so inclined. The pressure side gets a little more complicated in that you have to take the stock line coming out of the pump on the SOHC and route it down to the box then cut off the factory end and whatever excess line there may be. Once thats done take the line down to a local hydraulic shop and have them attach a new end on the line to attach to the high pressure port on the box.
Either way use 1/4" plate on both sides of the frame and run some tubes inside to sleeve the bolts so that they dont crush the frame in.
Check my build thread I think I have some pics in there