You would be better off getting your engine from an e34 mate! The sumps can be a nightmare to source due to the fact people know they are neaded to do this conversion and therfore charge lots!!
I got my engine from a rear ended e34 so the sump and pick up ect were already sorted. Keep your M20 starter motor, clutch, flywheel and fly bolts to, so you can ditch the M50's duel mass rubbish!!
Source a 318iS box so you can use your 320 prop and gear linkage, you will need an e36 328 rad and electric fan, e28 M5 rubber mounts (I payed £44 for 2 left hand ones in euro car parts), e36 engine arms.
Oh by the way, when you pull your 2.0 out cut the engine side plug off the engine loom but leave a good 30cms of wires to play with

. I hope this helps mate, there's prob small things I've missed out here but I'm quite tired rite now so do appolagise. Any questions feel free to ask mate, I'm sure someone else can add to this for you aswel -ant