Weighted shifts rod
Never heard of that before. Where do you get these from and also the headlight loom ?
Weighted shift rod is a mk3 item which adds weight to shift link meaning you get a nicer feel when you shift. They come up on eBay from time to time. Or I have one which I could sell, but not for a few weeks.
Up rated headlight loom makes your headlights brighter. Simple as that. Again you will find these on eBay, or can make one yourself if you are that way inclined, plenty of guides online.
Best mod for Mk1/2/3 imo with some good quality bulbs, candle power just does not cut it these days...
2.0 bottom end with PB head and fast road cam for 8v comes in second for me.
Removing big bumpers from pre 90 spec cars

The valver should just be restored OEM, polished with love and marveled at

280 4 stud brake upgrade is well worth it on all MK2's.