Did I order correct cam, man and carb?

[Old School Low]

Im having local machine shop slowly build a 383 for my 78 short C-15. New 5.7in rods Scat rot assbly is in. Hyper dished pistons but dont know est CR. Yesterday I went to Summit for cam pkg, intake and carb. I know just enough to get me in a mess Im finding out, so I went with Summit guys advice on almost everything. Going cheap as I could I ordered Howard Cam HRS-CL 110245-10 Hyd roller. 278/284, 500/510. Comp 17001 roller rockers, 1.5, 3/8. Comp springs 986, Comp retainers 740, Comp valve locks 611, Summit Carb 8750VS (vac second 750cfm) and Weiand Dual plane high rise air gap type manifold. Im using 1.94 worked over Vortecs. $1,435 for above and gaskets etc. Then...I got on line to see if what I ordered made any sense. I feel pretty good about all of it but have to have something to stress on and since I dont understand durations Ill stress over them...Im hoping for 4-425 HP, it will be 99% street driven but I want it to sound mean and go real fast. My big question: are the 278/284 #'s middle of the road or did I go way too high or low? He suggested 2500 stall and expensive fluid balancer. My book learned mechanic ability tells me the stall is ok but do I need expensive balancer? I will REALLY appreciate anyones comments and I have several ques bout how to post on this forum. I love being a part of it but dont know my way around AT ALL. My email is kennyq52@yahoo, hope someone has time to go there and explain this site too me. Would the $149 high rise without air gap style be just as good as the $269 one I ordered? (approx prices) Does my air need to be cooler than anyone elses?