What diameter does the fuel return line need to be (putting one in)? What is used on the 97-98's?
Can I just use good quality rubber fuel hose or do I need braided?

 

I imagine you'd be OK with fuel line rated for fuel injection. Normal fuel line won't hold the pressure. That being said, braided line would be preferrable.

 

The return line is not a high pressure line and doesn't necessarily need fuel injection hose although I would use injection hose just because it seems more robust. There is nothing pushing the return fuel so you do want a bigger diameter hose as well, 3/8 will work, but 1/2 inch is usualy recommended especialy if you have a high horsepower car. BTW, you can get fuel injection line from the local autozone and it does not have to be stainless braided line if you want to save a few bucks. Personaly, I don't like stainless braided line because it's difficult to work with and if it rubs on aluminum it scratches it all up. I prefer the pushlok hoses with the tough nylon carcass mixed with sections of solid line bent to fit and compression fittings. You can get solid stainless or aluminum lines. Aluminum bends much easier, but stainless doesn't squash so easily. It's depends on how much trouble you want to go through to bend the line.

Also on a side note, there are better grades of stainless braided hose. The cheaper ones don't last and can leak right though the hose. It's very difficult to spot, but you can smell it.

 

What is the pressure on the return?

 

In all honesty, I've never measured it. I've knocked one loose by accident on a running car and it more a seep than pouring out, where as an input fuel injection line leaking dumps a lot of gas in a hurry. I suppose you could put a pressure guage on it if you were really concerned about it, but I have run short sections of standard rubber fuel line on a fuel injection return line with no issues. This is probably something that varies a lot from car to car depending on the fuel system and engine demands. One of the aftermarket fuel injection kits I bought years ago came this way so I never really worried about it.

 

There is not going to be any pressure in the return line: It is open to the tank at one end! I have a braided -AN6 hose for my return line.