Price is decent. Put a second 50 on there. and then you would have 100 hp-if you wanted to go that way. Only problem is weight but current 50 is 205 to 215#. Current 90 is 359#, so it would be about 50# more weight. (Have to re-prop the current motor). Also the older 50 would be carbureted, and current is fuel injected. But it is do-able.
A new 50 in Fort Pierce FL is listed at $7354. You would need gauges, and new Binacle I'm guessing here, but I suspect you could get the setup installed for another $1,000 to $1200 with gauges, cables, etc. So ad $8,500--still be in a good ball park number for a nice 22. If you just want the slower boat--then. run it now.