Help! 72 Duster 340 V8 Exhaust Manifold

Right.
Someone had put headers on it & cut the transmission cooling tubes. When they replaced the cut out portion, they used plastic tubing. I'll replace this line, but won't do it before I get the appropriate manifolds.

Dad died when I was 3, so I didn't get a chance to talk to him about it. I know he had a beauty in mind cause my grandmother saved all his plans for me! And I know he didn't put on these headers cause they weren't in his plan & they'd be done right if he did. He was pretty much a perfectionist about his car from what everybody tells me. Thing is, I just want to drive it, not race it.