355 Blower eng. break in time n oil type q

[ABad84C-10]

Hello to all. I have just finished my 355 blower motor build. it has a 671 on it , hyd roller cam. comp is around 7:1 right now its underdriven until i get it broke in good which is partly my question to you guys. I am breaking it in on a conventional VR1 20W- 50. and plan to switch to synthetic. have only put about 50 miles on the truck so far tuning, tuning, tuning and bein careful making sure everything is good before i start runnin it hard. How many miles or hours should i run before the motor is broke in enough to switch to synthetic and what weight do yall recomend i run. this truck will be driven on the street every now n then but mainly building for the track.