Weber DCOE.
They are awesome when set up right and do not fall out of tune. The DGV is another option, they just work though do not look as cool.
I took two great condition and rebuilt CD175s off a B21 in a 144 and fitted a DCOE, it transformed the car once tuned. It started better, accelerated better, ran better, responded better. It was just better to drive.
I believe @iceton1975 (Mark I) has a DGV conversion kit at a really cheap price, I would suggest spend money on that before spending money on getting an SU working. Unless pure originality is a driver, then like Greg implied, settle in for a lot of learning and troubleshooting.
Get some electronic ignition too, it will make a noticable improvement to the starting and performance.
BTW: I think the differences in year model may have been the feature grade of the car, the DL was probably different to the GLE etc. Cannot be certain though, not my speciality.