Honda-SOHC

Anyone have a spare 400/4 points plate with the sub plate for points 2/3? My sub plate is a shocking fit on the main points plate and so adjustment is almost impossible.

Very interesting within Honda, is that they've built so so many different types in configuration and application, all good to compare design traits etc.

The three mentioned above all allmin the same area in regard to bhp per cylinder, more importantly loading (torque)  and speed all being close to specify a bearing for use in.

The detail in your thread about prototype 750, the small original big ends suggest it either started as a roller bearing crank or sized upward 8f origin in plain bearing, to control crank twist perhaps. 
Around that time were the car engine 4 cylinder too, with roller bearing crankshaft.

Yes, you'd definitely need a "depth" hardened surface to run rollers or balls on, thats in comparison to plain bearing arrangement.

That would mean you could regrind a crank, does anybody know if the journals are hardened cos i dont

If needing treatment after grind, process like this available https://aalberts-st-heat.co.uk/tufftride-qpq#:~:text=The%20Tufftride%C2%AE%20process%20of,the%20characteristic%20black%20surface%20finish. Suitable for materials that can't accept nitride treatment.

There are many ways to paint candy garnet brown.
I once saw a trick with a metallic brown base and a candy gold top layer. It worked quite well although it was a bit to brown in my eyes.
Easiest is a green metallic base with a candy orange top.

I use sikkens paint for the base paint and a German company for my candies.

And yes - always do a layer of clear before starting lines and black.