Any of the 3 stud Renault 5 wheels should fit the Renault 4. It's possible that 3 stud wheels from other Renaults will fit too.
The MK 1 (pre-1983 ish) Renault 5 engines will fit the Renault 4 gearbox. The automatic engines need a different brass bearing in the end of the crankshaft, but I think the others fit straight in. If your engine is good but you want more power try fitting the carburettor and inlet manifold from a Mk 1 Renault 5 1108cc. 10 more bhp.
I don't know whether the Renault 5 brakes will fit.