Thanks for the replies and suggestions. I think Swarfy is correct. I purchased the T/S bush about 25 years ago from C & D if memory serves me right. It is a composite steel backed item. The bronze?? clears the inside surface of the steel carrier by about 1/2 - 1mm, but I haven't measured it.
Also the steel carrier appeared to be scored, but not the case. It has only 80 miles on it sofar, so no real damage I hope. Oil pressure has been 60psi cold and 40psi hot. The carrier surface feels quite smooth. I haven't cleaned it yet, just scraped off the gasket material sofar. However, before dismantling the crankcase, I could not get any end float, so suspect there may have been a bit of pressure between the carrier and crank.
The photo was a bit too close up, so I have attached more distant ones. The scoring doesn't look so much. From 20 feet away, there is none at all.
I did think that it had a white metal liner, but it appears to be bronze. Failures were I think related to the inadequate pinning of the liner to the carrier.
As mine is well lined up and about 1.5 thou clearance between crank and bush, I will leave well alone and hope it holds.
Now back to the ball and spring, thanks John O'R for bringing that to my attention. I knew about it but hadn't considered it. But now rethinking, I am leaning towards doing what you suggest. John I do remember somewhere seeing a diagram of someone's modification, which suggested an additional diagonal oilway as there was some concern about the distance the oil had to travel past the ball before entering the bush. BSA - Bills website perhaps?? I will try to find it.
I haven't contacted SRM yet, but presumably they may also supply the extended plug.?? If not your dimensions will help me out.
Tomorrow, I will measure the dimensions of the passage depths and post them. My motor is very original, having been off the road since about 1975, so hopefully no-one has meddled with it.
Cheers
Colin