I started by mounting the transaxle to the cradle. The 4T65E-HD from the LS4 is much the same as those used with the 3800. The Fiero Addiction 4T65E brackets bolt on and fit up to stock rubber or poly mounts on the cradle, so that's a good place to start. The pictures below show the LS4 transaxle mounted to an '88 Fiero cradle using the standard parts from Fiero Addiction.
With the trans in place I was able to position the engine straight and level and begin making mounts. I chose to use two Energy suspension GM rwd trans mounts for the engine. After several mock-ups with cardboard, I cut the new mounts from 1/4" steel plate. The following pictures show what the final design looks like.
Mounting plates were welded to the cradle in two places to accept the poly mounts.
With the mounts complete at four corners of the cradle, the engine is secure. There should be no need for an upper torque strut, but one can be added later if needed.
