I’m sure this has been covered before, but is there a small output alternator I can get, that is a straight fit onto a ford 1600ohv block. The one which is on now is the original. All I need to cover is lights and ignition

Try searching for Nippon Denso in the archives.
They're small and light.

^^^^ but not a striaght fit though. most alternators, and hte one for the crossflow included, have two lugs in line on side that hold it to the block alllowing it to pivot, there is a third lug that goes to a bracket that is for adjusting belt tension.

the one mention has one of hte two lugs and then another lug in the middle on other side so you need to make your own bracketry.

there is an alternator that is a bit bigger then the one ^^^ but less then standard lucas one (I have weights) that is from a nissan with the same lug positions, I can post a piccy if I remember - can;t remember what it is from