Rear gear recommendation for highway.....

Wow you've spent a fortune on your setup. I'm learning on my 72 dart 340 .391 rear and 4 speed overdrive. I don't think the overdrive trans is going to work pops out of third and makes whining noise. Thought I'd buy a four speed rebuilt from Brewer's they've helped me a lot. I'd be neat to have it done by someone you trust. Think I asked them once and they told me $1300 +freight. Then I was thinking of a 3.23 center in my 8 3/4 to cruise. Switch over to go draggin.