I do not think that many SOHC4 owners also own a DOHC4 of your vintage. Many of the Chinese repro insulators do not last long with issues cracking or breaking down. Some have reported when exposed to fuel with ethanol or straight gas, which a carb may occasionally do if you have some issues or the bike end up on its side.
Better to pony up for real OEM Honda in most cases. Originals likely lasted for what 38 years? That is not too bad a lifespan...even 20£ or £80 for a set of new intake rubber over 10 years is not that huge an investment.
