Depends on what he is wanting. Frame? Performance? Maternal? Calving ease?
As far as what to go after and/or stay away from everyone has their own opinion and then the next guy will totally disagree with you.
Here is what I think some of the better bull ines to follow for maternal:
Rambo(several sons and grandsons availble)
Example - Rambler 5162, Red Rocket, Powersurge, etc
Barney
Run Cloud
King Rob(several sons and grandsons available)
Example: Dakota Copper
Logan
Hobo
Grand Canyon
Performance:
King Rob (several Sons and Grandsons available)
Example: Rattler, Data, Vaquero, Robin Hood, etc
Advance
Design
Monu 4X
Calving ease:
HLH Buster
LMG Custer
Jr 107
DKK Addiction
Hobo 1961
Heavenly
BHR Logan
Their are more for all catagories, but this is just what I can think of off of the top of my head.
I invite you to check out my website to take a look at what I feel are some pretty good Reg Angus cattle.