I am thinking about having a 700R4 tranny put in my 55 210 Chevy. It now has a TH700 in it but I think it's seen better days. I am torn between the 700R4 or a M-20 but what I need to know is what would be the best the rear end gear for the M-20, give me the take off power but decent highway speeds as well. I was told the car has 3:55 gears but I have my doubts. It does not shift twice if I take off in drive but it will if I use it as a manual valve body but after it hits 3td it acts as if it needs another gear bad. So what would be the best gear for the M-20? I've heard of changing out the third member but being new to this I don't know what that means even though I think I do. Thanks for any help.