I have Enya SS40 (both BB and plain bearing), new and used (by others). In the pics, the one in the box is a new, plain bearing, with my second hand plain bearing besides it. I'm trying to decide which of these to put in a Kadet Mark II that I'm building. The other two are ball bearing versions, one of which I broke in last year and the other is used that I bought on e-bay.

I want to run/break in three that I haven't run before. Fuel: Omega, 5%, and I've added castor oil.

I'm planning on using a 10x6 for running/break-in (rich for a couple of tanks, stopping every two minutes or so, some throttle changes).

I bought some A3 and #8 OS glow plugs (I have a Enya 3, but only one) to run.
Is one of these going to be better than the other?

Suggestions / Advice?

Also, is there anything that I should look out for with the second engines (one bb and one plain bearing?)

Thanks!