Freaky,
The top forks are Canam betor. Steering stem (I think) should be 1" OD top & bottom. It maybe 25mm but from memory its 1" (good old USA hasn't gone metric yet, & Jeff Smith of course is british). Mine are on the bike now so I can't check. Offset (centre of stem to centre line of forks) should be 60mm.
Champion frame headstock could well be imperial dimemsions too (since also made in US). Timken taper catalogue lists numerous 1" ID bearings available, a couple w metric OD, but most w imperial OD. If you meaure yrs & post/pm them, I can look them up for you as I have a catalogue.
The others appear to be for forks w offset/leading axle. Probably w 36mm tubes. If they're Suz (& I suspect they are too), offset is something like 30mm. See what VMX42 is getting at! Forks w in-line axle typically ran 52-62mm offset back then (except for post73 Bultacos).
I don't know what triples/offset champion frames were built to use. (Did any of yr frames come w triples so you can check?) But if they were built around the typical 52-62mm offset triples, reducing that to only 30mm would give you more trail, a heavier feel to the steering cos of more self-centring effect & more weight on front wheel, & a shorter wheelbase. That may mean the front wheel sticks better, but it may also completely stuff up the geometry & handling.
If they're Suz/RM forks, stem OD is probably 25/27 (top/bottom). Go to Allballs website, where they list ID/OD of all tapers (in pairs) that they sell, or let me know as I've downloaded their info & I'll check for you. Or try Pyramid-parts.com in UK if you don't find a match. They sell them individually too.
Hope this helps