transfering mods to another engine

I will be buying a 180sx soon and i was wondering if whatever mods i do to the cars engine, would i be able to transfere them later on to an s15 silvia
they both have the same engine.
the mods im talking about are things like polished ports, hollow pistons, chrom piping, intercooler etc,boost control, turbo timer, and then bring the 180's engine backto stock.

also will this cost alot to do, can a simple mechanic do it?

the reason i wanna do this is to save me money, and i dont wanna do a full engine swap because when i buy a silvia i want the engine in as new condition along with the car.