The VKA has a fixed-throttle and automatic choke; in theory, you could replace the those parts with a manual throttle and choke, but unless your old mower is also an HRR-series unit, it's unlikely they would fit.
Sames goes for the Roto-Stop (blade clutch). Unless it is off another HRR-series model, it won't fit. I'll guess your older Honda with a blade clutch was an HR or HRC model maybe? Totally different engine/crankshaft/etc. from the newer HRR models.
If your old mower has a GXV engine, it has a cast-iron sleeve and can be rebuilt. Parts are usually available, and lots of people would pay a fair price for a strong-running older Honda. How bad is the old engine? Are we talking big gaping hole in the engine block or just worn rings/smoking a bit?