If you use 5/16" fuel line (hard line) like I did, the fitting flared onto it is a 1/2-20 inverted flare. These will work for both your radiator and transmission, assuming they're stock:
GAR-48IC5X2 1/8 NPT to 1/2-20 Inverted Flare 5/16 Hard Brake Line Brass Adapt | eBay
1/8 NPT to 1/2-20 Inverted Flare Fuel Line Brass Adapter 90 Degree 5/16" Tube | eBay
1/8 NPT to 1/2-20 Inverted Flare Fuel Line Brass Adapter 45 Degree 5/16" Tube | eBay
I just used the straight one personally.
EDIT: Here's a pack of them for a great price:
5 Pack 5/16" Female Inverted Flare Tube x 1/8 NPT Male Pipe Adapter Coyote Gear | eBay
Note-- I wasn't able to bend the line all in 1 shot. I had to splice it together with a short piece of regular 5/16 fuel hose. If you run into this just use a line beading tool or put a little flare at the end of the hard line. Secure both ends together with a short piece of 5/16 fuel hose and use good tight hose clamps.
