Personally I think you are wasting time with a greddy intake manifold, stick with stock unless aiming for well over 500kw then go for a plasmaman or hypertune or something similar.
Didn't see you addressing oiling anywhere in your post, I would pull engine, enlarged and gated sump plus billet gears, baffling and restrictors in head with a good catch can. Head gasket and studs along with the fuel you mentioned and ecu. Then beat on the standard bottom end until it goes, with oiling and balancer etc it should last awhile and hopefully will be ring lands that fail not bearings meaning a cheaper rebuild.
While it's out replace a heater hoses and do major service etc, get covers painted, all fiddly odds and ends.
As others have said if going above a -7/9 size range ditch twins.