For yur combo the iron intake is perfectly fine actually better than most alums for ALL ROUND performance in the 350-400 hp area. If you can change a starter and install a dizzy you do not need a shop to do any of the things most folks have stated!
Degreeing a cam ...time consuming PITA but when it MATTERS....well it matters. only need 3 tools total tool cost about $75 and TIME
Checking the balancer for timing mark correctness ....again easy peezy just like changing spark plugs 1 special tool ...$20
For a simple motor there are MANY folks who can walk you thru a BENCH build/check of YOUR Q-jet that will get you running VERY well. Parts choices ar a bit difficult to find NOW (I think) but still available
BTW glad to see the deck height ###'s to kinda confirm the compression ratio
(note the 041 cam recommends 10.5:1 + on compression)
The RAIV cam in a 455 is almost SMALL then you are only using the 1.5 rockrs makes it SMALL with a long duration. you should have torque out the wazoo but your your hp will be a little late to the show. Consider the RAIV is .469 lift with 1.5 rockers YET the ACTUAL RAIV used 1.65's which netted ..513 lift...on a 400 cid....you can see this cam is a bit small when you add 60 cubes..BUT still a great runner!
So now I think the big question associated with the ask is
PLEASE DESCRIBE LAZINESS OFF THE LINE?
If you have a 2800 converter and 3.73 gears.....unless you are running 11.5 slicks and a 2 barrel with caltrac's......you should NOT BE getting TRACTION! if you hammer it.
I don't think you need to go nuclear with a set 310 heads single plane intake MSD ignition....%^&*( you just have some parts that are NOT tuned together