Not sure on injectors, there is one way they work but not the other.
Personally I'd want pump / injectors / pipework to be honest.
Electronics, this could be fun as the anti theft module if fitted may well be different for Bosch vs Lucas. I've not yet checked this (I can with some more info) although it would be sensible to dearmour the replacement before fitting if possible if nothing else to save headaches when you find out the texton you currently have does not like the 'replacement' pump module.
Bosch pump sometimes has some coolant pipes on it for advance when cold, Lucas does not (appear) to have this. Not 100% sure on the fitment of this into a 306/ZX though may of been only for electronic advance (aka 406/Xantia) units.
306's , series 1 (K to early P) were Bosch with turbo and mostly Lucas without. series 2 (P to T) were 99% Lucas with turbo and Bosch without.
Intercooler, I was not aware the ZX TD did not have one, the thing to bear in mind is its atop the engine so you'd need to arrange some airflow. Take a look at the underside of a 306/405 bonnet to see what I mean.
TUD's, well keep well away from the elderly alloy 1.4 unit (only fitted to about L maybe early M reg) , its very slow and noisy and I think it 'feels' fragile. 1.5's actually quite reasonable although you do have to work them a bit, its best to think of it as a small petrol engine as torque seems to be a bit higher up the rev range than you'd expect from a diesel.
Expect high MPG. Mines such that I have not bothered to check it. At a guess its around 50 to 60mpg, possibly more I'm not really sure but I don't drive with heavy boots. Having said that on a 106/Saxo you cannot easily press it all the way down due to the pedal arrangement and where your feet naturally rest, could be me though.
EGR very very rarely gives concern on these (90% of 1.5's have EGR) it is very easily disabled by simply either removing the plug from the valve on the bulkhead of removing the vacuum pipe (plug it, I plugged mine at the servo 't' piece using a leakoff cap) , usual EGR nasty what appears to be an inlet manifold oil leak rather than running issues.
Quite reliable and easy to put right. Only downside is the engine bay is a bit tight for space. Pump/Cam have three bolts to adjust so not as straightforward as an XUD to do the belt but not really a problem to be honest.
Oil leaks can be caused by overfilling later models it seems, Andy suspects bigger capacity to cope with extended oil intervals may be the concern here. Its OK as long as its not overfull. I run mine around 4/5ths (leave about 5mm below the 'max' line) instead of completely full to the mark. It does not appear to use any oil either now.
Later (2000 on) TUD's are electronic pumps like the 406/Xantia 1.9TD, large ECU sits ontop the battery. They are very reliable I have one. Economy seems about the same, the only two downsides to this unit (TUD5B) compared to the earlier ones (TUD5) are nosier cold running (simply as there's no cold start cable and it plays with the timing to keep it running) and hot starting not 'instant' due to the timing not being mechanical, compared to the TUD5 earlier unit, still stars after two seconds cranking though. Seems to be normal.
Note killing EGR on these electronic ones will log a silent fault, to avoid this do not unplug the electronics just blank the vacuum and that's that. 'k' light will not come on for EGR fault anyway nor will it enter limp mode either.
EDIT... Tidied post and added a bit more info.
Andy.
91 205D-Turbo, gone but still missed
02 106D, TUD5B, gone but not really missed apart from the MPG