his 92' already has the stronger 7.625" rear in it with the 28 spline axles instead of the 7.5" with the 26 spline axles. you are right about the TQ arm and the control arms. before i started drag racing my current set up i had a 355 putting out about 390-400hp, I upgraded to a 7.625 rearend from a 91' and I never had any issues with it.
think about this, how many LT1 and LS1 camaro's are out there with a set of headers and exhaust, reprogramed, with an aftermarket intake and just some other bolt on mods. these cars are making about 400hp and still using the same 7.625" rearend. dont get me wrong these rearends are week and will likely be the weakest link on the car with 400+hp/tq but i've seen plenty handle this kind of power without any problems. its the 7.5" rearend with the 26 spline axles which is so much weaker. after saying all this, i must say that with my old set up on my 385, my 7.625" rear didn't last 3 weeks. but it was also putting out 490tq.
I am someone who believes saving the money and doing it right the first time so i understand what you are telling him. I just dont think that is what he looking for. for many people 400hp in a street car is all they will ever care to have. based on the parts OP picked, i assumed that he was on a budget that is why i suggested the iron RHS 180 heads, and believe it or not they actually flow 258cfm @ .500", these numbers came from an independant shop that has flow tested hundreds of different heads on their SF600. most $1000-1250.00 alm heads are right in that range with them so how much would that extra $200-450.00 extra for the alm heads acutally benifit him. they are lighter, but if he's not racing then the extra 50lbs will never be seen nor felt. now for the heating aspect. the alm heads will be easier to cool, but as long as he has a decent electric fan he wont have any problems with the irons heads, on my previous motor set up i used Dart 200cc platinum iron heads and i never had any issues with keeping the motor under 190°.
Yes, would a set of AFR 195's, Brodix IK200's, or Dart pro-1 200's along with a hyd roller cam be his best option for making more power, absolutley. with these he would likely make 50-75 more hp all day but he would also spend another $1500.00 doing it.
Sometimes you have to make recomendations based on what you believe the OP wants, not what you would want.