4l70 transmission line fitting to stock radiator size

[NurseBen]

Hello, I'm about done with my ls/chassis swap from a 2011 GMC Savana AWD van and would like to use my stock 1969 radiator with the newer push-clip in style lines that came with the van. Having a difficult time what size works, does 9/16 - 18 inverted female to 1/2 - 20 inverted sound right? I would love to use the stock van radiator but the filler neck is about 5" tall and would hit the hood. I've also been looking at a 2000 Cadillac Escalade radiator for about $100 but if I could just buy a couple of adapters for the old radiator to the new lines that would be ideal. Thank you for the help.