ZF 8HP Swap
8HP45 from a N55 (N55 8HP45 cross-compatibility). If you choose to use an 8HP45 from a 20i or 28i, the output flange will not need to be swapped like mentioned below but the internals are also theoretically weaker. If you opt to use a 8HP50/51/55 from a B58, you will need to use an adapter plate from Domiworks or PMC. If you want to use a 8HP70, it needs to be from a diesel model which is very limited in the US so you would have to import it from Europe which gets quite costly and needs to be paired with a Domiworks/PMC adapter plate. You cannot use a 8HP70 with a V8 bellhousing yet as an adapter plate doesn't exist. On the bright side, the adapater plate makes up for the difference between an 8HP45 and 8HP70 (~15 mm) so the transmission mount part number listed below works perfectly.
8HP oil cooler adapter - HTG, Domiworks, or HPR-Tuning
Oil cooler - Get something that's high quality. This transmission does not like high temps. I went with Setrab 50-619-7612 along with the fittings of your choice and smooth lined or spring loaded hose clamps. I opted to go with barbed fittings as the price for AN fittings + hoses gets expensive fast. I went with Derale 15799 for my transmission cooler hose as you get quite a lot for a good price. If you go with the same hose as me, use IDEAL TRIDON 5310 clamps.
Thermostat - I opted to go with Improved Racing's High-Flow Inline Oil Cooler Thermostat, 165°F FSM-165. From research, it seems like a lot of cheaper thermostat have problems and this is something you don't want to have problems with.
Fluid - I went with TOP TEC 1800 ATF - Liqui Moly LM20032. You can use Lifeguard 8 Automatic Transmission Fluid but it's pretty expensive.
Filter - 24118612901 (This is only for 8HP45 and 8HP70)
Sealing sleeve - 24147588896
Shift selector from any BMW that has fully electronic shift selection - the selectors are pretty easy to find from part outs. I opted to go with the selector from a DCT F80 M3 (61317848611) because it looks better.
N54 8 bolt flywheel - 11227553157
8 x N54 flywheel bolts - 11227522125
N54 starter - 12412354701
Automatic M54 dust plate - 11142243305
TCU of your choice
Drill bit (size TBD) to oval out the top two holes as they don't line up with the M5X bolt pattern
Grab the output flange from any of these cars with an automatic transmission that have a 6HP or 8HP but must be from a non-35i model as those use a 110mm guibo (we need 96mm) (so E90 and newer for 3 series, F10 and newer for 5 series although E60 might work as they also have a 6HP but the part number for their guibo is different):
24207552327 seems to work fine
Cross-compatibility for 26117511454 (credits to Geroge W. Hill)
Transmission bushings - 22316799331
Transmission mount -22326767985
If you don't get a transmission from a 1, 2, 3, or 4 series, you also need the mount that bolts the transmission 22326796613
E46 M3 SMG Paddles with harness -
32347833040 (switches)
32347891003 (small paddles) or 32347891004 (large paddles)
Clock spring - 61318379091
You need to use a clock spring from a newer E46 as it already has a provision for the connector for the paddles. You can check by removing your airbag and looking at the first connector slot. If there are no pins, you need the newer style.
Solder in PCB for the transmission - You can purchase this from Ryutech but because he ships from out of the US, you can go with AutoRevGarage (ARG 8hp Mechatronic PCB Solder Board for Turbo Lamik TCU-ARG)
Some p-clamps, hose sleeving (if you're not using AN line), and hose separators to keep things nice and clean
Automatic E46 ZF 5HP19 driveshaft -
26111229564 for 4 bolt output flange
26117505211 for 6 bolt ouptut flange
34mm 12 point deep socket for removing the output flange nut. I couldn't find one deep enough according to my measurements so I went with Proto 5342 (1-5/16" 12-Point Deep Length). You can see in the image comparing Tekton's deep socket the Proto deep socket.
The reason you swap the output flange is because all the cars that come with 8HP that make a decent amount of power use a guibo that is either 105mm or 110mm. E46 guibo is 96mm and that matches up with the lower models of said chiassis' above. This allows you to use a stock E46 ZF 5HP19 automatic driveshaft. The driveshaft has some adjustment to it which works in our favor. You can also use an E46 M3 guibo which pushes the driveshaft back 6mm due to being thicker.
The starter on these newer cars is bolted to the engine rather than the transmission like our engines have so you can buy an adapter from George W. Hill to work around that hurdle. (Demonstration of adapter)
By using the transmission mount from a Z4 (part number above and huge shoutout to George W. Hill over at Hill Performance Bimmers for discovering this. Make sure to support him by buying his adapter)), everything is plug and play.
Credits to all the efforts put in by others in the community that tackled this swap first. George W. Hill, Paris Argyrides, and Timothy Steinert