Lost53 you would be better off to change the rear end gear or the complete rear end to achieve what you want. I changed my 53 ring gear and penion to a 3.55 and gained the highway speed you are looking for. Later a friend gave me a 55 1st complete rear end and I went with that and a over drive transmission and now I cruse 65 to 70 with ease.
If I had to do it over I would go straight to the over drive and rear end first. That 235 is not a screamer but it just purrs down the highway now.
Tom
