Hi Scott,
If you can start with a '06 up engine they are much better. The head is significantly better on the exhaust side and they have better rods in them (which I recently found out). Also the '06 up motors have built in oil squiters to cool the piston domes.
The tooling to make a rear sump oil pan is out being made with initial pans hopefully cast before years end.
Steedspeed makes a turbo manifold for this engine. Bigger injectors are available.
I ran 8 PSI on my early 4200 and inspection of the block on inspection show no ill signs.
Currently running a modified '06 with sleeves, rods, pistons. The '06 head is ported with custom cams on 10 PSI its a brute.
https://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=40140#Post40140EFI
