I'm not building a FFR Cobra but there are quite a few of us starting to use the LS1 & T56. There are about 4 people I know currently building or have built LS1 powered Cobras.
Personally I think the LS1 and T56 is an excellent choice for a Cobra power train.
One thing I might suggest though is that you go with an IRS. The T56 is such a long transmission that you may run into difficulties with tailshaft angles using a live axle.
Cheers
