I converted my 1993 +8 three years ago to the Mulfab ball thrust bearing conversion with the 140 lb/in springs. I found I did not need to use a compressor at all - just drop the axle stub as far as will go through the hole in the bottom mounting, fit the spring and top tube over it. Then by bending the spring (pull the middle, push the top) you can start to get the top of the spring/tube under the top mounting. Then a good shove gets it in place.
I put the king pin in next, up through the bottom, while the spring is easy to move around to the correct position, and put the top bolt in.
I did it with the calipers and hub taken off, but I don't think that having them left in position would alter any of the above.
You could leave the bronze plate in, but the whole point of the conversion is to get rid of it. If you leave it connected to the spring steel blades, then the ball bearing becomes redundant and you are in effect using the old system. However, the bronze set-up does give more friction, and if you begin to suffer from shimmy, you may prefer to go back to it. So you could put the bronze plate in and leave it disconnected, but make sure it doesn't hit anything, eg shock absorber, as it rotates with the stub axle when steering. And then you could re-instate the flex blades if you wanted to without having to strip it all down again.
Good luck!
