Thanks for all the info peeps!
I have talked to a guy that I bought a few kits off a couple weeks ago and he has an AMT 70 Monte Carlo with a 454 and auto in it so will get that from him. Then I can still build the kit later with one of my other engines. The 50 just really needs to be an auto!
As for the 53 from revell, I have an early one of them and it has the 348 chev with a rather dodgy looking auto yes, and the 54 panel has the same engine/trans I believe but is stated as being a 409.
But it still doesnt answer why AMT has stated they have an auto in the kit when it is clearly supplied with a muncie 4 speed?