I have a Series 5 with minilite wheels and 185/70x13 tyres fitted and are finding the steering VERY HEAVY and almost dangerous in some situations. Can anybody offer advice on what to use to convert it to electric power steering. (It has the adjustable steering column.)
Did you check the tyre pressure? I had the same experience with my Rapier Series IV with also minilites 13 inch, but after some time I found out that the tyre pressure was very low and after rectifying this the car was steering normal again. Anyhow this cars don't need to steer that heavy and fitting power steering is working around the problem without solving it. There are more possible culprits than a low tyre pressure! Jack up the car at the front and start with turning the steering wheel in order to find out if this turning is going to heavy. Other possible cullprits are for instance the steering idler and the swivel bearings.
I run mines on 2.5 bar and all is well. I know that greynivek has already mentioned his troubles with the steering in 2018 on this forum, but he never answered with feedback. It looks like that he is doing the same again now and that is very disappointing. People on this forum try to help each other and the least someone can do when asking for help is responding on suggestions. It is a matter of being polite or not.