Two piston sets are available, hypereutectic and forged.
Big pistons require case machining and head machining, but the stock cooling tin still fits.
Any stroked crank beyond 78mm requires machining of the case beyond that which is required by the larger cylinders. I located about a dozen aftermarket cams for 914s, and each producing company seems to have at least one specifically for Big Fours. I heard from several sources that it's important to use lifters from the same company as the cam comes from. Big Fours have a reputation for short lives, and the cause of death is usually related to excessive heat buildup. Assembly Problems with parts.