Fit the block? I know the RWD L36 mounts are different then LT1/LS1 mounts in an FBody. People who swap to a V8 from a V6 Fbody have to change motor mounts and K-Members. Not sure if it would be easier to get RWD 3800 Engine mounts and then fabricate or just make mounts from scratch.

Just an FYI as far as the transmissions go you only have two bolt on options. I 3800 4L60e or a T5 with a 3800 bell housing. The 3800 is not a standard SBC bolt pattern and won't bolt up to a TH400, TH350 ect unless you make a bell housing adapter.

Edit: The 3800 Series II block is much different then the old 3.8 Turbo motors that came in the GNX's and T-Types. The 3800 Series II is also much different then the 4.3 V6 since those are basically a SBC.