C3 Rubber Transmission line size

[Sheldon S.]

My 71 BB car with auto trans has the original steel lines from the tranny to the front near rad. The two adapter lines that go on the radiator are repo. the steel original lines to tranny measure exactly 3/8 where the rubber hose goes on and the new adapter lines that go on rad measure 11/32. I had 3/8 hose on and have fought trying to stop the leaks where rubber hose go on the adapters. Ordered a kit from Zip, new lines are 5/16, they will go on. the new adapters but can not get them on the 3/8 lines.
Any suggestions greatly appreciated.

Thanks
Sheldon