Alright this is what my engine builder told me and is also what my dad and his mates (one who is 3 time National Pro Stock champ who built his own engines) has confirmed.
Note: This will vary from engine to engine, ring type to ring type and application to application.
Engine: RB25DET, Chrome-Moly rings and forged pistons (Venolia) unsure of exact clearances but pretty tight as on cold it will generate 4-6kgm2 below 3000rpm when cold on 5-40 Pennzoil full syn.
Run in procedure:
First 100km, use proper full mineral run in oil, vary revs keep loads up do not exceed 3,000rpm, ie keep it off boost as this helps the bed in and reduces the change of bore glaze. During this time I also disconnected the turbo timer just in case. The hone on the bores was also reasonably rough/deep compared to stock hone as we were using the moly rings. Drop oil and change filter
First 100-1000km's repeat process above.
1001km - 3000km - this step is not really necessary, however depending on clearances, tollerances ring squish etc may be helpful in an exellent bed in and further reduces the chance of blow buy and poor piston bore bedding. Drop oil and change filter. Another option is semi-synthetic, something like Motul 4100 turbolight 10-40 would be ideal if using standard rings or non-moly ones.
3000km, at this time I went for a semi-synthetic at this stage however, if you have done this between the 1001 and 3000km range then go to a full synthetic or maintain the usual oil changes on the semi. Depends on the engine builder's recommendations.
3001-5000km, changed to full synthetic Pennzoil 5-40 (I think it may be 5-50) upon recommendation from the engine builder. All cylinders have compression within a range of 5-7psi difference depending on gauge, perfectly bedded in and runs like an absolute dream!!
The additional point I want to make is...
IF YOU ENGINE BUILDER CANNOT RECOMMEND A RUN IN PROCESS, FIND ANOTHER ENGINE BUILDER!!!!!!!
On another note, street engines have always been run in a longer process than a race engine, these or often done on the dyno but involve just as many oil changes!!!