ouch! You ran lean at part throttle and your egt's must've been cookin.
I don't understand how you went past 5800 rpm without a programmer...did the valves float on yah?
rebuild with a forged/billet crank, H-beam rods, and forged/billet pistons. cam is optional, but if you want more power, scour around for a custom turbo grind. Cams with negative overlap are excellent for turbos. Just tell the supplier/cam grinder what kind of power you're lookin for, and if you want more low end /mid range/higher rpm.
Might as well get those heads cleaned up . No doubt there will be dents and dings in the combustion chamber(s). You want those smoothed out because sharp edges will glow hot during operation and possibly lead to preignition/detonation. You can always buy a set of performance heads, and trade in your cores. You can buy bare heads or complete with port job, larger valves and stronger springs and pushrods etc...
Hemi Shop, Sharadon performance, Frank Racing, Ross pistons, Cp pistons, are all good companies.
Don't cheap out on parts, It'll bite you in the ***.......
Then after all that........you'll defenitely have to upgrade the transmission. Its lasted this long for you, but don't be fooled, the clutches won't last long. Sharadon Performance has performance 545 transmissions, and their latest creation, the 58 rfe hybrid, which has diesel components inside the 545 case
it sucks when **** breaks,.....but at least you have an excusde to rebuild