The mains were removed without drama and replacement seems straightfoward apart from the drilling of the new front bearing through its holder with two extra oilways (no problem!!!) Here is the drama!!
I have knocked out the retaining pin, which needs to be reinserted through the bearing holder and into the new bearing.
The pin is 4mm wide,15mm long and the bearing is about 2mm thick. I know I have to drill so as to ensure that the pin can go into the bearing but not through it,(drilling and reaming required) and that the surface of the pin is at least 1mm clear of the bearing surface.
ME 109 has discussed the process with me at length, but it's still causing sleeplessness!!!

Can I make a grub screw to secure the bearing? Make a new pin with some interference fit?
In knocking out the staked original pin, I have nothing left (alloy) to securely peen the pin into position!!! Locktight? Dob of ally weld?
Help!