Re: [Chevelle-List] trans

[MICRLASER]

You will need to have your driveshaft shortened and use what is called a "junk joint" for using a TH400 yoke on a TH350 driveshaft.  The yokes are specific to TH400 tannys.
TH350 uses a cable kickdown whereas a TH400 uses an electric one.  You don't really need to have the kickdown installed on a TH400, manual kickdown works just fine :-).  I have a TH400 in my 70 and have never had the kickdown hooked up, I just manually drop it in 2nd when I need to pass someone.  Your crossmember is the same, just have to relocate it back 4 inches, there are holes pre-drilled in the frame. 
I don't think I am missing anything else here, but if I am, someone else will chime in.

Tom