Those motors are pretty stout. If you look at the M10 motors (4-cyl in all the 2002's and 320's/e21), the M30 motor is literally an M10 with two extra cylinders. Or the M10 is an M30 with two fewer cylinders. Same rod ratios (bore to stroke ratios), same oiling, same pistons, valve sizes, cam profiles, etc.
A lot of guys will put baffles in the M10 pans to help with oiling or sump pickup. If you can weld I'd recommend making the sump as big as you feel comfortable. Stupid shit on all those cars go --stuff like driveshaft center support bearings. Weld an O-Ring around the d-shaft CSB so if it goes out mid-race stuff doesn't come up through the floor. Same with the flex disk (guibo) between the transmission and the dshaft. Do yourself a favor and weld a ring around that too. Whatever you do, don't reuse flywheel bolts or head bolts on a BMW. Ever.
If you guys have the budget for the wire, stitch welding helps a lot (not seam welding, that'll warp the frame, calculated stitches to keep the body panels tight). That'll keep your suspension geometry solid. Front & rear strut top mounts are huge. Fronts can be failure points. Not sure I'd go solid but maybe see if you can find the budget to replace with at least new OEM. I'd do new OEM and slot the strut towers over spending the $$ on adjustable camber plates.
Water pumps and tstats are huge. idk much about the m30 but in the m10 & m20 motors guys drill out the tstat but keep part of the housing to restrict flow. You need the coolant to flow slowly across the radiator or else you won't pull the heat out. Lots of guys just ditch the tstats and have overheating issues. Some people weld their oil sprocket nuts. I usually drill them and use safety wire. Water pumps and belt fans are ticking time bombs, especially with suspect engine mounts. Usually you can ditch the manual fan and run electric AC fan only.
Do you know about www.realoem.com? Enter your VIN and it'll give you exploded diagrams of everything. Do you have an automatic or manual?
Vacuum lines are a royal pain in the ass on those cars (that vintage). Tear out as much as you can --but don't be dumb about it. Make sure you know what you are taking out and why. Don't over-rev it. Some of that throttle body housing coolant line crap can go but some of it has sensors associated with it so just pay attention and don't tear everything out. Those rocker arms LOVE to break. Keep the RPMs down. If you can afford it, a rev limiter might be smart in case someone misses a shift. Depending on what rear end you have, if you are ballsy, a lot of guys will weld the diff. Rear driveshafts are a dirty, nasty pain in the ass to rebuild (to get the balls back in) but easy, cheap and straightforward. Most of the time you can reuse the boots. If you can weld/fabricate you can lower the cars well and mess with rear geometry easily. Some model cars had issues with rear diff carriers failing. not sure if your car is one of them but Google it.
That's a big, heavy car but pay attention to weight and balance. The motor is heavy and as you gut it, make sure you don't end up with too much weight up front. Bump steer will be a bitch and they can get tail happy.
Physically pull out, remove and then put the emergency brake lines back in the tubes with lube/anti-seize. They can build up rust and shit in there. Last thing you need is a hot parking brake to heat up a rear wheel bearing or rotor.
Oh --also, BMW is weird with transmission and power steering pumps. They run weird fluids (like ATF in some power steering pumps) in weird places. It's probably worth a flush just because.
Watch out if you need to weld around the area where a mud flap would hang off the front left quarter panel. A shit-ton of wires run down the driver's side right there... Easy way to start a fire before you get to the track (ask me how I know this .
I'd make a bigger oil sump. Maybe 2-3qt bigger (think about cornering and oil starving). Then over-fill your oil by a quart or so. Everyone runs full or a little over-full. Lots of guys build battery boxes into rear strut braces. Again, not sure what your team budget is. Pretty easy/cheap to fab up something. That'll keep weight back too. Clean out your timing chain tensioner.
Sorry that got long. Kind of a brain dump. Hope it helped. Keep in mind when you race, slow is fast. That's a really stout motor. A well sorted car should get you through the weekend. Then it's up to the driver from there. Hmm... What else... Don't be afraid of welding up cheap/ghetto solid tranny mounts but don't mess with the engine mounts unless you know the arms are solid.
Happy to answer any questions. I don't know it all but I love BMWs...