Today was monumental. Got a whole lot done in 4hours!
Because the E30 parking brake cable did not fit into the E21 tunnel, I simply tacked it together. I'll paint it later.
I welded the radiator mounts. Will be painted later. 
So day 4 I got the S54 in the car. Lifted it by traditional means with a hoist. It wasn't all that bad getting it in. I needed to cut the front radiator shroud area to get it fit. Please note that this is NOT the final resting place. it will get pushed back at least another 4-5 inches.
Below, I installed the front half of the driveshaft. I already got the rear half in and aligned to the E30 subframe. That already defined the center bearing location as shown in Day 2. Now that it's sitting suspended as shown, I can place the engine and mate it to the driveshaft. Once mated, the engine is now in place.
It took no more than 45 minutes to get the engine in. It's sitting much further forward than I'd like (aka the driveshaft and transmission are way off and the engine needs to sit further back).
As of today, the S54 is sitting on the subframe, unobstructed and the trans bracket is installed, but will need to move much further rearward to mate to the driveshaft.
I didn't do too much with the subframe. Just grinded it down, but no welding today. Stay tuned for tomorrow! Garagistic has some pretty sweet 80A mounts that I plan to use that will allow it to sit exactly where it will live with minimal movement and minimal vibration transfer. 
Got the exhaust setup ready to go. Days 6-8 will be reserved for welding of the downpipes, the muffler, and the midpipes. 
I welded the exhaust hangers up a bit better today. I welded lips on the exhaust stem so that the hanger sits right in the center and doesn't move side to side on harder cornering.
I also welded studs for the rear subframe lower poly hold-down brackets. I did this because the E30 subframe is wider and the subframe was actually hitting the bracket weld-nuts. So I removed the weld nuts from the brackets, I welded studs from the inside flush, and will now bolt the bracket on the OUTSIDE of the body. The only thing I need to do is elongate the subframe bolt.
Removed weld nuts in this pic...
Welded studs (countersink screws) from the backside pointing outward. 
I need to clean these welds up, but the idea is that now the E30 subframe will not hit the body due to it being wider than the E21 subframe. 
Thanks for reading. Standby for more work tomorrow as we set this drivetrain in it's final resting spot!
