It has a 4 bolt mains already and vortec heads. What else does it need? to be a 383 it will need a new crankshaft. connecting rods, etc.
You can run the factory 5.7" rods, The pistons will need to be swapped (Higher wrist pin height). You can also run 5.565" 400 rods but new pistons are still required.
383 is technically a .030" overbored 350/327 (4.00") block with a 400 3.75" stroke crank, We used to turn down 400 cranks before companies like Scat started offering cast & forged cranks just for this.
The increased stroke may not the best thing for a marine engine that spends its entire working life at higher RPM's, Sure.....If it's balanced well & you use top shelf Forgings, It may last longer than the original 350. Use bottom of barrel cast crank, Recon forged or powdered rods, & Cast pistons....Don't expect much in the way of longevity.