If you use the 91417 Steering Block from the ProSC10, you will likely also need to use the (71127) front axle from the ProSC10 as well … I am thinking the T5m front axle is not long enough if I remember correctly, I know the B5m wasn't and the T5m axles are a direct fit replacement through the stock steering block (length) …
Funkydrummer, what # inserts have you been using? … being the 2/4 is by far the most commonly used with 4 being the stock setting, there is probably an abundance of the 3's floating around in boxes … I probably have some, if that helps you at all ...
The other thought, is if the bearing fits well, the inserts itself can get sloppy, and many simply add a drop of glue to fix it solid ...